I could be wrong but afaik showtime is after
initialisation which is part of the sync process.
Theres 2 states of connection - syncing to the exchange and then PPP session, the later being out on to the internet via your ISP.
Most routers will record 2 sets of uptime. The time the router has been up for and the time its held a valid internet PPP session.
Actual uptime displayed as LAN uptime doesnt normally allow for any loss of sync, but the time the router has remained switched on for.