Index 4208 for 95 a-m FoV


The field of view of my imaging gear is 126x95 a-m (x, y).

If index files up to 4213 are available Ansvr solves wit 4210 (FoV 60 to 85). I would expect it to solve with 4211 (FoV 85 to 120 a-m). If only up to 4208 are available it solves with 4208 (FoV 30 to 42). I would not have expected a solve with index 4208 for my FoV.

Why the two index files can be used to solve for 95 a-m FoV? How are these index files constructed?