Cranking set to 'trigger return' - problem?

[o.g.johnson]

I've just tried the trigger return feature, and have strange numbers in my datalog.

Ignition input is VW 4cyl distributor, trigger offset is 83 degrees btdc. Trigger is the beginning of the 'window' so voltage going low at this point, inverted of course by the optoisolator to give a going high trigger. Ignition input capture is therefore set to 'rising edge'.

Cranking trigger is 'trigger return'. The window is approx 80 crankshaft degrees wide, so the engine is at tdc just after the end of the window (just after the hall signal goes back high) ie just after a falling edge is seen by the processor.

Log file shows 83 degrees spark advance during cranking, but it surely can't ACTUALLY be 83 degrees or it wouldn't start at all, just kick back against the starter. So my question is, is this a normal thing to see during cranking with trigger return selected, or have I got something set up wrong here?

log file attached, thanks in advance