I know C bucket is for SWU upgrades and U bucket is for milesaver biz award. If I see U3 and C2 for a flight and I grab the 2 C spots for SWUs, will the U bucket tick down to 1 or is that independent of C space (and remains at 3)? Ideally I would like to buy 2 eco tix and apply SWUs and also get 3 milesaver biz awards on this flight. Hoping someone has experience and can share.