I have no idea what I did wrong.  Or even if I did anything wrong.  After clicking "print label" and choosing printable postage with DC,  I entered the weight of the paperback as 7 oz., anticipating to pay for and use the Media Mail rate.  Then I adjusted the mailing date for tomorrow's date and printed the wrapper.  A little later, when I started wrapping the book, I then noticed the postage was for FIRST CLASS mail, not MEDIA MAIL.   Before I taped it, the book weighed 6.9 oz. and even though I skimped on the mailing tape, the book now weighs 7 oz..

What can I do?

How much is the postage for First Class?  For 7 oz including DC  it should be $2.33.  Media Mail would be $2.31.  So it's best to mail it First Class, don't you think?

Since the postage changes, the postage is printing out what the founders think is the better deal, not always media mail.

LB