The addition formula of abacus calculation is a text summary used to guide the action of plucking pearls and perform operations. "Up" means to dial the counting bead against the beam, "Down" means to dial the counting bead against the beam, "Up" means to dial the counting bead to the side, and "Middle" means to add a number to the front position (the first left gear).
The first word of each sentence in the formula indicates the number to be added, and the last word indicates the number to be dialed.