How many sessions required for FUE scar coverage by SMP? (Photo)

I've had 6000 FUE grafts in total, I've approached various SMP providers in UK. Most providers here charge the same price per session but I've been quoted different numbers for sessions required; ranging between 3 to 6 sessions. How many sessions would it take to do this? I am worried because I don't want to do an insufficient number of sessions and also I don't want to do too many!