1) In your new number function you're using Array Cur Value condition incorrectly - it only works in conjunction an Array: for each XYZ element condition.
2) The repeat may pick the same co-ordinates twice so you may only get one number in the array.
3) Using int(0,3) won't pick 3 and may put a number on X=0 so when you slide it will disappear off the array.
Here's an example that I think gets closer to what you're after:
Note that this only works if you're sliding to the left - if you change the slideX value to positive then there's a chance you can overwrite values as you slide, due to the order in which the For Each XYZ element condition proceeds.