Hello Mike
When you say you have a 240 volt branch circuit in that room and it is on a double pole about the only thing that could be is a multiwire branch circuit that has a shared neutral. Are you familiar with that? Unless your talking about a special branch circuit of some kind for a specific appliance.
Second for clarity are the baseboards 240 volts or are they rated 120volts? It is very common for 1000 watt heaters like this to be 120 volts.
If you have a multiwire branch circuit it will look like this at the breaker panel.