There is no limit to the number of applicants a program can rank.
Programs do not have a limit on the number of applicants that can be ranked on the rank order list (ROL). Rank all applicants who are acceptable to your program to avoid having unfilled positions. But remember, the match commitment is binding so rank only those applicants who meet your program and institution requirements and are acceptable to train.
If you are creating a lengthy ROL, consider creating an electronic file containing applicants’ rank numbers and NRMP or AAMC ID that can be imported into the R3 system.