efiled, but TT says I have to also print 8949?

After I efiled my federal return.  TT popped up a message saying I have to print/mail a "US Individual Income Tax Transmittal for and IRS e-file Return" (form 8453))   That form in turn says I need to print and mail form 8949.

 

Not sure why I need to mail that form specifically?  Not sure if the message from TT is accurate and wonder if it will this just create confusion?  Has any one encountered this before?