Electrum allows you to create any number of
deterministic addresses that are based on the initial seed. You could have done something that asked for another deterministic address; press "new address" on your offline PC and it will likely be the same extra address.
I cannot find the new address button.
OK this worked:
typing this in console:
wallet.accounts[0].create_new_address(0)
I should have searched before but kind of freaked out!
I did not know that could get more addresses in Electrum.
Super cool!