The original Hotkey icon size is 36x36. The default for this set is 27x27, which is exactly 75% scale.
The 4 pixels of padding around each button has not been scaled, resulting in an overall window size slightly larger than 75% scale.
General feedback seamed to indicate this was the smallest most users wanted the buttons. Many felt it was too small, so I included 85% and 100% scale versions.
You're more than welcome to upload a smaller version (skinned for Fetish) as an add-on
