When you fail with feeder cast you get +1 stat point when you reroll.
So I passed to samurai, after 7 fail, and it took the 3 plus stat point. If I would reroll it to mage, then I will have 14 stat point I think, and if
I reroll again to samurai then it will take again the 3 stat point what it was taken already?

iso answer =)

are you talking about potions? or the stats that u put in for the failure of the character?

if you are talking about potions then if u fail a mq as a feeder class then ur stats will be back to its base, but ya recieve +1 extra stats for failing

if you fail as a samurai then you'll receive +2/etc for other characters after a samurai

so are you talking about if u fail as a samurai and wanting to reroll a mage back u get an extra +3 stats? i have not tried this yet but many others will know

i've tried it and it tooks 3 stat point to reroll after passed mq to mage
but if you reroll from mage to samurai it won't takes extra 3 stat.

Starting stats work with the following formula

(10 + #fails/#passes+1)