If you upload the .fzz file of your sketch, I’ll try it on 0.9.3b and see if I can figure out what is wrong. For me (as you see in the images) it accepted me typing 255 over the default 24. You may have to backspace over the 24 (so the field is blank) before you type the 255. It may feel it already has 3 characters for some reason.
Peter