The Repeat action allows you you repeat a sequence of sub-actions as many times as you like.
The repeat count can be a simple number, or you can use a variable or other calculation in the field (as with most all numeric fields in Keyboard Maestro, simply start typing and the field will expand to make room for more than a number).
The Variable Repeat topic on the wiki shows how to ask for a repeat count and then repeat a set of actions that many times.