It seems to be working correctly, since Con bonuses don't apply to your vigor points according to Ultimate combat pg 206 "Creatures with one or more full Hit Dice or levels gain vigor points. With each level gained or each Hit Die a creature has, it gains a number of vigor points based on its Hit Die type. Use the creature’s Hit Dice to generate its vigor points, just like you would hit points, but without adding the creature’s Constitution modifier."
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