Hello KipFoE,
So did you fully paid the Bloodline package or is it on layaway? If its on layaway you should first paid it off for that Bloodline package.
If you have already paid it off than you select the Mayor package and you will only pay the difference. So If you already purchased a Bloodline for amount of $125 than to upgrade to Mayor you will only have to pay additional $125 which will give the total $250 (which is the amount for how much you can purchase Mayor Package for at the current time)