(1) There are three types of first class mail -- letters, large envelopes (flats) and parcels.
(2) I never send chips using the "large envelope (flats)" rate because I feel the mailpiece is always rigid in places and uneven, so I assume it will be kicked up from "large envelope (flats)" rate, to "parcel rate."
(3) going by your chart, the 4" x 7" bubble envelope wouldn't qualify as "large envelope/flat."
(4) thus, the 4" x 7" mailpiece (if over 1/4" thick) would be charged at "parcel" rate, which is $1.13 for the first ounce (and 17-cents per ounce for additional ounces up to 13 ounces).
(5) you can all have fun looking at the post office regulations, tests and pictures of the Physical Standards (rigid tests, unevenness, etc.) of the first class letters, flats and parcels here:
http://pe.usps.com/text/dmm300/101.htm#wp1039555+

Hope I didn't make errors here. If so, I'm sure to hear from readers.

Robert