Number: 2 (coarse) 34 (fine)
Whatever the musician sets this controller to affect. Often, this is used to control a parameter such as what Aftertouch can. After all, breath control is a wind player's version of how to vary pressure. If a MultiTimbral device, then each Part usually has its own Breath Controller setting.
14-bit coarse/fine resolution. 0x0000 to 0x3FFF where 0 is minimum breath pressure.