Comment 1 for bug 936979

Agreed, ideally it would go from zero to infinity. It’s just difficult to find a suitable widget for this, see e.g. the usability issues zoom sliders in many applications have.

I will try to find a better solution in a future version. If you want to fix this quickly for yourself, just open data/ui/TranscribeWindow.ui, search for "<object class="GtkAdjustment" id="adjustment_speed">" and edit "<property name="lower">0.5</property>" to match your needs.