$724 for package 1 plus 11% tax= $724 + $79.64 tax= $803.64 for package 1. Package 6=$1300 w/o tax so, $1300-$800(package 1 w/tax) =$500 (plus tax not included yet). So, You are upgrading to a package $1300. Tax on that is $143. The difference is the packages is $500. IMO this is not the correct way to calculate this. The tax should not be added to the $724 to get the difference w/o it being added to the $1300 in the same calculation. To get the $639, she took the $1300 and added the tax which is $1443. Then she subtracted the $724 plus tax ($79.64) which is $803.64. So, she took $1443 (total package w/tax) and subtracted $803.64 (total package 1 w/tax). That brings you to $640. This seems accurate IMO. The problem seems to be that the two coordinators are not on the same page as far as how to calculate charges and credits. I think it can be very confusing so I get why, but clearly there is a miscalculation on someone's part. I am leaning more towards Cri's not being calculated correctly. She can't add the tax to one and not the other when calculating the difference. I'm upgrading to special package 1, but I am double checking and there seems to be some type of problem with the math there as well (could be me though!)