why there is so many volume change event in short interval as pulseaudio rewind the stream when volume change

Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] ratelimit.c: 346 events suppressed
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 65429 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 65377 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [pulseaudio] module-device-restore.c: Storing volume/mute for device+port sink:alsa_output.pci-0000_00_1b.0.analog-stereo:analog-output-headphones.
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 65103 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 65072 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 65054 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 65030 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 64973 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 64942 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 64915 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.189|   0.000) [alsa-sink] sink.c: Next volume change in 64890 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.190|   0.000) [alsa-sink] sink.c: Next volume change in 64749 usec
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.006) [pulseaudio] protocol-native.c: Client indicator-sound-service changes volume of sink alsa_output.pci-0000_00_1b.0.analog-stereo.
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] alsa-sink.c: Requested volume: 0:  75% 1:  75%
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] alsa-sink.c:            in dB: 0: -7.66 dB 1: -7.66 dB
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] alsa-sink.c: Got hardware volume: 0:  75% 1:  75%
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] alsa-sink.c:               in dB: 0: -7.60 dB 1: -7.60 dB
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] alsa-sink.c: Calculated software volume: 0: 100% 1: 100% (accurate-enough=yes)
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] alsa-sink.c:                      in dB: 0: -0.06 dB 1: -0.06 dB
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] sink.c: Volume going down to 48850 at 3644251579
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.196|   0.000) [alsa-sink] sink.c: Volume change to 51472 at 3644251579 was dropped
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.197|   0.000) [pulseaudio] module-device-restore.c: Storing volume/mute for device+port sink:alsa_output.pci-0000_00_1b.0.analog-stereo:analog-output-headphones.
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.055) [pulseaudio] protocol-native.c: Client indicator-sound-service changes volume of sink alsa_output.pci-0000_00_1b.0.analog-stereo.
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.000) [alsa-sink] alsa-sink.c: Requested volume: 0:  71% 1:  71%
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.000) [alsa-sink] alsa-sink.c:            in dB: 0: -9.09 dB 1: -9.09 dB
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.000) [alsa-sink] alsa-sink.c: Got hardware volume: 0:  71% 1:  71%
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.000) [alsa-sink] alsa-sink.c:               in dB: 0: -9.00 dB 1: -9.00 dB
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.000) [alsa-sink] alsa-sink.c: Calculated software volume: 0: 100% 1: 100% (accurate-enough=yes)
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.000) [alsa-sink] alsa-sink.c:                      in dB: 0: -0.09 dB 1: -0.09 dB
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.252|   0.000) [alsa-sink] sink.c: Volume going down to 46228 at 3644321423
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.253|   0.000) [pulseaudio] module-device-restore.c: Storing volume/mute for device+port sink:alsa_output.pci-0000_00_1b.0.analog-stereo:analog-output-headphones.
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.254|   0.001) [alsa-sink] sink.c: Volume change to 48850 at 3644251579 was written 20 usec late
Mar 12 19:13:48 pbcombat pulseaudio[1888]: (  35.254|   0.000) [alsa-sink] alsa-sink.c: Written HW volume did not match with the request: 0:  75% 1:  75% (request) != 0:  74% 1:  74%