I am a little confused in what I am seeing in my shopping cart. Basically I sell two different kinds of products; CDs and LPs. I have them both with their correct weights and both ship in different boxes. When someone buys a CD the shipping shows up correctly (approx $1.75) . When some one buys an LP the shipping shows up correctly (approx $8.00). However when someone buys a CD AND an LP the shipping shows up at $6.35 which doesn't seem to make sense as the LP alone would be $8.00. Any idea why this is happening?