Rate plan extra guests

When setting the rate plan for extra guests the assumption would be from the way the form is laid out the each extra guest would amount to the total charge of the room booking
eg guest one 100 so box 2 for second guest would be the total plus the amount for the second guest so if there was and extra charge of 10 the box would be entered as 110. I now realise that each extra guest box is only the charge for the extra guest eg box for guest 0ne 100 box for guest two 10 which is fine but it does need to be clearer when adding the rate plan.