Noticed this the other day and can replicate it directly
(Mac OS)
Open LB and use the rectangle tool to make a box.
Try to resize with the % boxes using the up/down buttons.
The size does change in the dimension fields but the % fields stay at 100%
I can enter % numbers directly onto the fields and get the desired result, it just seems the up/down % buttons are not updating the % number fields.
That’s how it works. When you use the up/down arrow keys the new size is 100%. If you want an exact percentage reduction or increase, type the number into the box and hit enter. The item will resize and it will read 100% at the new size. The boxes always read 100% after a change.