Double Cycle/Loop Length   ⌥⇧⌘.

Doubles the cycle length. The cycle area is lengthened in a forward motion. This becomes important if you change your mind and want to ‘Halve Cycle/Loop Length ⌥⇧⌘, — Halving shifts the start of the cycle forward in time. The only way to make the cycle smaller leaving the start position alone is by moving the cycle end mark backwards

Use the cycle area in Logic Pro — Apple Support

You can use the cycle area to repeatedly play a particular part of a project. The cycle area can be used for composing, practicing a part before recording, recording multiple takes, and other purposes.

Change loop settings for cells in Live Loops for Logic Pro — Apple Support

Loop Length: Determines the length of the loop. Changing the Loop Length value can be useful when you want to loop only a particular portion of a cell.