Your random number should be in the range of 0 to the number of children in the variable minus one (because arrays starts at 0 you need to subtract 1 from the count)
See this similar example, I used sprite name instead of just numbers:
Edit: also, you need to move the remove variable at action down. It’s currently deleting the element before the value is read. So, it reads a different number. Get the value then delete the element.