Grid/Collection Stitching parameters




I am trying to stitch grid form images but still confused with Grid/Collection Stitching parameters.
I’m not sure whether ‘Tile Overlap[%]’ meant for maximum overlap or the approximate overlap.
If I set the overlap value as ‘20%’, will it search area between 0~20% or 20%-uncertainty(%) ~ 20+ uncertainty(%)?

If the uncertainty of overlapping region is quite big, such as 5%, where should it be appeared?
I’ve changed overlap and displacement parameters to various settings but some tiles are aligned way outside it’s location.