Cell-counting factor that limits the maximum size of the multicellular structure. Does not possess acid phosphatase activity. Cells with decreased levels of this protein form large groups while cells overexpressing this protein form small groups. Component of the counting factor (CF) complex, which includes cf60, cf50, cf45-1 and ctnA. Expressed in the vegetative cells and decreases during subsequent developmental stages (6-24 hours). Cells die quickly. Belongs to the histidine acid phosphatase family.