Carryover volume is volume that can accumulate on the powerleg over time. Carryover volume or bank volume is calculated by subtracting the weaker leg volume from the stronger leg volume. The remaining volume left over after subtracting is the carryover volume.
Keep in mind carryover volume will either be on the left or the right leg NEVER on both legs at the same time.
Carryover volume will ALWAYS be on the power leg or the "stronger leg".