The phrase "number off" is often used as a command in military or group settings to designate a specified order. However, depending on the context, other synonyms can be used to convey the same message. For example, in a classroom setting, "count off" or "line up" could be used instead. In a sports team setting, "take a position" or "form a line" could be used. In a musical ensemble, "arrange yourselves" or "take your place" could be used. Ultimately, the most appropriate synonym depends on the specific context and the desired level of formality.