This is the maximum number of Call ID entries stored in the node's Calling Identifier table, which itself can hold up to 512 entries of 30 digits each. An admin sets this to control how much of the node's memory or table space is reserved for tracking distinct calling-party identifiers, balancing the ability to recognize or screen a larger set of known callers against conserving table resources for other node functions. For example, setting this to 100 reserves room for 100 distinct 30-digit calling identifiers to be tracked, well under the table's 512-entry hard limit.