User blog comment:Mich, Michele & Kuhla/Guide: UBB and the OD gauge/@comment-66.108.48.168-20150615211343

Mechanic posted above states that starting from 0. Each units actions will fill the OD gauge by the amount listed. Depending on what you do each turn you'll fill between 1200- 3000 pts of the OD gauge.

Furthermore each time you use OD, the amount of points needed to use it again increases by 5k until a max of 40k. First time use = 10k, by the 6th time and more it'll cost 40k.

Once OD gauge is completely filled you can ONLY DO ONE UB. It doesn't matter how many 7 star units are in the party. They all share the OD gauge and once OD is selected for any one unit, it is to the exclusion of the others.

note: OD = overdrive