I don't know for sure, but I'm thinking it's to keep track of how many outs they've recorded.
10-Team H2H Std. 5x5
R. Martin, G. Atkins, J. Rollins, A. Hill, D. Wright, A. Gordon,
E. Renteria, Crawford, M. Ramirez, P. Burrell, N. Markakis, C. Hart
Lincecum, J. Cueto, H. Street, G. Sherrill, M. Capps, AJ Burnett, Putz, B. Myers, Harden, Bedard,