Yeah mate this happened to me and I was very worried to say the least! It turned out that the Seaway invoice was to cover everything, including the other out-dated invoices I had received. Basically the most recent invoice from Seaway (the most expensive one ) is all-inclusive (or should be anyway).
Also, if you had any inner cargo as I did, do NOT let Seaway handle the pack&send of it as they will overcharge you outrageously. The quote they gave me was 1000% more than the price I ended up paying after doing some research.
EDIT: whoops should have read the second page! Sorry for rehashing.