http://ai2.appinventor.mit.edu/reference/blocks/math.html#randomint
It would really help if you provided a screenshot of your relevant blocks (i.e. the random integer block), so we can see what you are trying to do, and where the problem may be.
To get an image of your blocks, right click in the Blocks Editor and select "Download Blocks as Image". You might want to use an image editor to crop etc. if required. Then post it here in the community.
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.