This read-only integer reports how many channel ports are available on specifically the first span of a multi-span telephony board, which can differ from the port count on subsequent spans depending on framing/signaling overhead. Admins use it for accurate capacity planning on boards where the first span isn't identical to the rest. For example, an ISDN board might reserve a channel for D-channel signaling on its first span, giving it fewer usable voice ports than gwPortsPerSpan reports for the remaining spans.