This break point represents the maximum number of pieces you would sell before you would ship the customer an entire case. The value of the break point can be set to equal the number of pieces in the case
If there are 6 pieces in a case, and a customer ordered 8 pieces, the system would convert this to 1 case and 2 pieces (two separate line items on the invoice).
Or if your break point was set to 5 pieces (for a case that had 6 pieces), and the customer ordered 5 pieces, the system would change the order to 1 case (correct pricing would be used).
Related to the use of System Option 21 "Convert pieces to cases in Invoicing."