Office mode means that:

 Office mode is a feature that allows a security gateway to assign a remote client an IP address from a network that is protected by the security gateway. This way, the remote client can access resources on the internal network as if it was physically connected to it. The IP address is assigned to the remote client after the user authenticates for a tunnel, and it is routable, meaning that it can be reached by other hosts on the network. Office mode is useful for scenarios where the remote client needs to use applications that rely on IP addresses, such as VoIP or file sharing12.

References: 1: Support, Support Requests, Training … - Check Point Software 2: Gaia R81.20 Administration Guide - Check Point Software