Health not working with ''_min'' tag

Invalid
It's "score_Health_mind"

{score_Health_mind:6s} Does not work.

also {score_Health_min:6s}

you put it completely wrong, use:

/scoreboard players set @e healthbar 9 {Health:6}
/scoreboard players set @e healthbar 9 {Health:5}
/scoreboard players set @e healthbar 9 {Health:4}
/scoreboard players set @e healthbar 9 {Health:3}
/scoreboard players set @e healthbar 9 {Health:2}
/scoreboard players set @e healthbar 9 {Health:1}

or use these:
/scoreboard objectives add Health health
/scoreboard players set @e[score_Health_min=6] healthbar 9
because what you tryed is putting a scoreboard selector argument in a data tag

So, how do I get the mob in the health scoreboard then?

just damage it, or heal it
forgot, Health scoreboard only works on players, you got to use the top one

because datatags are absolute, there is no "_min" posible

Well, thanks for you time.

but, is there an other option to keep track of a mob his health?

nope

Lets hope they will add something like that in the future 😛

sorry, got to end this, this is a bug tracker, not a forum