Please note that the values are not adding to each previous level.
Example: the "+10", "+15", "+20" next to the Fighter Slots are not adding up together. It means that with VIP 2, you will have 110 Fighter Slots, with VIP 3 you will have 115 Fighter Slots, with VIP 4 you will have 120 and so on.
The "+" in the VIP level descriptions means how much is being added to the initial level, not to the previous level.