When discharged by 30 ampere in 5 hr then its capacity is 150 AH (30x5) at 5 hr and abbreviated as 150 AH C5
When discharged by 15 ampere in 10 hr then its capacity is 150 AH (15x10) at 10 hr and abbreviated as 150 AH C10
When discharged by 7.5 ampere in 20 hr then its capacity is 150 AH (7.5x20) at 20 hr and abbreviated as 150 AH C20