Palemaster Spell Duration

[a shrouded figure]

I figured out how the bonus spells work- however palemaster levels do not appear to affect spell duration for hexblades.

3 hex 10 pm I’d expect expeditious retreat to last for either 3 rounds + 5 rounds or 3 rounds plus 1 round. It didn’t change with 10 levels of PM, and only lasts for 3 rounds