How does -mana regen work?

So i got a pair of alternators off the trade market, and it has this tag.
what does this mean, do i lose 11 mana each second, do i lose 11 mana every 4 seconds or how does this work?

 

you lose 11 mana over the course of 5 seconds

 

I see thanks
ill prob sell it then

 

btw i think it only triggers once you enter combat or start castinf spells

 

It triggers when equipped. Mana steal however only triggers when you main attack an enemy