Guild Wars 2

So Celebration booster is +10% it says. XP booster is 50%. At 195 level of participation I should get 60% increase for 312 right? But, I’m just getting 292 which is 50%. Do these two things not stack? Intentional? Cap at 50%?

Guildhall wvw track booster will add up to 312, celebratory or birthday booster don’t work for some reason.