LaRosch writes

See, in the picture, the highlighted field.

Linux Mint 18.1 x64 Cinnamon

EDIT: ah, I find that this problem is intermittent; sometimes everything is of readable size.

medoc writes

I just can’t reproduce this at all (in a VM). In any case, I think that this is a standard Qt spinbox, there is not much I can do about it (increasing the default size would then make it appear strange in the normal case).