Okay let's do the math.
If the membership was 10,049 as stated and the turnout was 71% then the number of actual voters was 7,135. The number of those rejecting the offer is said to be 81% which means 5,779 BASSA members voted NO to BA's offer.
The number of NO voters represents 57.5% of the BASSA membership. That's hardly an overwhelming majority.