While working through my initial implementation of EAS Build, I set my Android versionCode to say, 11. Then I switched to using autoIncrement alongside appVersionSource = remote, and EAS Build is incrementing from say, 5. There should be a way to inform EAS that I want auto-incrementing from a certain minimum version.
I imagine this would also be necessary for projects migrating to EAS Build which have an existing set of build versions. Similar considerations exist for iOS of course, just using Android as an example here.