@aibd cited the documentation at (answered) Install /e/ on FP5 with newer Security Patches - #2 by aibd in full, the examples should give you a good intuition?
In the unlocked mode it doesn’t matter, but once you want to relock, if the patch level (android security patch date - not android version) is behind what was last recorded during the locked state, you’ll brick the phone.
Note down your patch level date and wait until /e/OS supplies a release past the patch date on any Android Version you want, then you can safely relock.