Reading the model code
B1A- Family segment. The 1A here is the balance-current class, not a pack rating: what governs JK-B1A20S15P is 1A active balancing, and the class comes with the family rather than being chosen separately.
20S- String ceiling, about 64V nominal on LiFePO4 cells. Take the cell count from the pack, not from the model name.
15P- Continuous discharge position. The spec table on this page lists 150A, and that is the figure to size cable, terminals and the protective device against.
What actually changes between these codes
Same current, different ceiling: JK-B1A24S15P runs to 24S where this board stops at 20S, which is 4 more cells in series. Choose on the cell stack, because no setting converts one into the other.
JK-BD6A20S15P is the other candidate for the same pack: 20S, 150A, 0.6A balancing rather than 1A. It sits US$7.25 below this listing at the base configuration. If the cells are matched and the duty cycle leaves idle time, the cheaper of the two is the right answer; if they are not, no protection setting replaces balance current.
On price inside B1A this listing sits at 3 of 4: US$86.38 for the base configuration, against a family spread of US$71.16 (JK-B1A8S10P) to US$86.98 (JK-B1A24S15P). Configuration add-ons shift that position, so compare like-for-like variants rather than headline figures.
JK-B1A20S15P is listed in 3 configurations. JK-B1A20S15P at US$86.38 against JK-B1A20S15P+4.3"Display at US$121.36 is a spread of US$34.98, which is the figure to weigh before assuming a bundle is cheaper than sourcing the add-on separately.