Comment 5 for bug 311828

> Path > Stroke to Path. The Property Bar shows now 30,277 x 30,277 mm.
> Is it normal to change from 30,282 to 30,277 ?

I think that's a different issue, involving another conversion factor that might lead to rounding errors? I get different values: sometimes it's 30.286x30.277mm, other times 30.277x30.286mm. It isn't a square anymore after applying 'Stroke to Path'.

repeating your steps with: all units set to px (internal unit, needs no conversion)
1) draw rectangle 100x200, stroke 10px (to better visualize)
2) resize with rectangle tool controls bar width&height fields numerically to 100x100
3) switch to select tool, size shows correctly 110x110 px
4) apply 'Stroke to Path' -> size stays at 110x110 px

There are other bugs related to the numeric precision values, like
bug #190557 “resize of object or group by entering a numeric size results in a different size”
bug #370137 “"Geometric bounding box" setting does not affect XYWH edit fields on the Tool Controls bar”
but they can be reproduced without unit conversion happening (all units in px)