What kind of numbers are we talking here? Not having flown these sectors or seen the bidding process I have no idea.

And how are day of departure upgrades different? Are they the equivalent of what British Airways calls AUPs? Does JAL also do an equivalent of what BA term a POUG?

Context for those terms here:
https://www.flyertalk.com/forum/brit...thread-10.html

and here:
https://www.flyertalk.com/forum/brit...24-thread.html