This says 2 things, and 2 things only:
1. 7-5 teams must fill a conference's bowl slots before it can select 6-6 teams from that conference to fill that slot. (IE All 7-5 sec teams must be placed in bowls before selecting a 6-6 SEC team)
2. A 7-5 record gets selected before a 6-6 team with a contingency agreement.
Nothing is mentioned here about 6-6 teams except as it related to 7-5 teams. Unless the SBC's contract with the Independence Bowl specifically states that the SBC representative has to be 7-5, or unless contracts don't mean anything, this is a no-brainer and the Independence Bowl will have to take a 6-6 Sun Belt team over any other 6-6 team.
This doesn't take a degree in rocket science. You only have to slow down and read.