OpenSprinkler 2.3 and 3.0 can detect the number of expanded zones (though in the current firmware you still have to manually select the number of zones because the number of zones doesn’t have to be the same with the number of physical zones, since some zones can be ‘virtual’ zones like HTTP or RF zones).

OpenSprinkler Pi does not have circuit to detect the number of expanded zones, so you just have to go to Edit Options and manually set the number of zones. So yes you have figured it out.

Some of the document links may have been outdated since we transitioned from opensprinkler.freshdesk.com to openthings.freshdesk.com. Sorry about those outdated links.