The double mana tick?

[Crenshinabon]

Hello everyone!!
Back first time in many many years. I have been having a blast on my currently level 22 Paladin. The community has been so awesome. Run into people leveling everywhere. Somehow I meet others new to P99 still. Pass it forward was said to me once.

ANYWAYS, enough gushing.

Question about mana regen ticks.

Normal mana regen I assume as follows (also after reading wiki)::: 1 tick per 6 seconds server time. It appears there is also a client tick that this may work off instead?

What confuses me. Is after I heal, if i sit immediately, I almost always get TWO ticks of mana regen. If I use other spells besides my heal, I don't always see the double tick.

Do I not get this "extra" tick of mana unless I am sitting? It makes me feel like if I don't sit in between each cast, I lose a TON of mana regen potential.

I was hoping to confirm the best way to do this, so I am not over doing it and sitting when I don't always have to.