> ...
> sometimes i have to add empty "" for that to work and sometimes works without it :/
> ...
Although Construct tries its best to convert between numbers and text, you are free to explicitly convert to text with the expression 'str':
AppPath & str(random(10) + 1) & ".png"
This should work without exception.
Ampersand concatenates to string, so it should automatically be converted.
I've seen others use the plus sign, and it worked, but I can't think of a situation where that method would be better.