I feel like I'm missing something obvious, but I cannot find the answer in searching.

Booked a flight in B on UA with one segment on LH. Requested upgrade with gpu and am waitlisted. Looking at expertflyer they show:
J9 C8 D7 Z1 P0 Y9 B9 M9 U9 H9 Q9 V9 W9 S9 T6 L0 K0

So question is what does UA B upgrade to at LH? J, C, D, Z, or P?