This is one I don't understand:

HNL-PHL on Jan 11 via ATL
Connecting on DL1218 (7:30am to phl):
DL836
F9 P0 A0 G0 W9 Y9 B9 M9 S9 H9 Q9 K9 L9 U9 T9 X9 V9 E0
DL1218
F9 P9 A0 G0 W9 Y9 B9 M9 S9 H9 Q9 K9 L9 U9 T9 X9 V9 E0


Connecting on DL1220 (8:45am to phl)
DL836
F9 P1 A0 G0 W9 Y9 B9 M9 S9 H9 Q9 K9 L9 U9 T9 X9 V9 E0
DL1220
F9 P9 A0 G0 W9 Y9 B9 M9 S9 H9 Q9 K9 L9 U9 T9 X9 V9 E0


So, the HNL-ATL segment is P0 if connecting to the earlier flight that has P9, but on the next flight, the same HNL-ATL segment is P1 with the same P9 on the ATL-PHL segment.

Why would it be P0 with one and P1 with the other?