The "B" next to the altitude means the altitude is calculated on Barometric pressure, an R would indicate Radar altitude.25010 = Altitude in feet
B = ?????????
"TAC" or "TACT" refers to the main menu type, i-e either "Tactical" or "Support" (SUPT). (TAC) contains options for combat-oriented systems such as radar and stores management, and (SUPT) is used to access non-combat functions such as navigation and maintenance modes.