that means that either the item is configured wrong, or your plugins are messing with the engine.
to check both options, please give us a screenshot of the item in the database, and screenshots of your plugin manager listing all plugins and their order.
then we can check for the possible causes.
and the item shows the reason why you got the wrong marker
The plugins you're using most probably default to HP if there is nothing set in the damage formula.
I suggest setting the damage effect to "MP Recover" and use the damage formula instead of the effect window, that should solve your problem.
A surprising number of plugins have appeared for MZ since last year. I'm currently making a "shopping list" so that I'll know what I need to test when I switch over to MZ later this year. Much of it is stuff updated from MV plugins, but there are also a good number of new things. It'll be fun to test it all out.