JDE E1:34 Planning Time Fence days and it's relationship with Leadtime level

ref doc- E1: 34: Planning Fence Rule and Days, Freeze Fence and Message Display Fence (Doc ID 655578.1)

Leadtime for the Parent SKU is 20 days. With Planning time fence rule of C how many days in the planning fence days are recommended that I set up?

To note that this below is our timeseries horizon

and also if the lead time is 10 days with the planning fence rule of C how many days in the planning fence days are recommended that I set up?

PS- I ask this to know what is the precise relationship of planning timefence days with its lead time? Because