Battery decay isn't linear. What it means by 3 times as long is that normal conventional laptop battery have an average life cycle of 300 cycles. The new ones have 1000 cycles, 3 times as much.
What Apple promises is that the battery will have at least 80% original capacity for up to 1000 cycles on the new batteries.
My current 4 year old, original 300 cycle battery has 65% health still and holds over 1.5 hours of charge at max brightness/100% cpu.