Problem with Combined Shipping

[mawstreasuresga]

A buyer requested to do combined shipping on two items. I sent them an invoice and somehow it showed them less than what I put. I couldn't ship the items because it wasn't enough for shipping. I sent them a new invoice and they now says it shows even cheaper than before. I don't understand why it shows me one price and it shows them a differnt price. 

I've used the calculating tool with both of our zip codes to come up with a better combined shipping cost. I'm at a loss at what I should do now. Please help!

[pooh333piglet]

Well its hard to know what you are looking at when you send the invoice to the buyer. You can combine the sold listings and be sure both are shown in the total price. Then I thought you can add the ship cost and before sending preview the invoice. I am not 100% positive here but trying to help. Maybe someone will come along with exact info

[mawstreasuresga]

I do use preview and everything on my end looks right. I'm a begginer and don't know how to do this. She is more experienced but has never done combined shipping before.