Set max limit

[tnanhkhoa]

Hi jose!
I like and respect your work. I replaced your example images on digit number images (0,1,2,3,4,5,6,7,8,9).
My question: how to set max limit of it? For example: 500 and when i press the button, the result is less or equal 500, no more 500 (505, 876)
Thank you!