in the bottom center of your DIC display, you'll see one of three: D (drive mode, shifter towards the left) S# (sport and current gear number, v6's have 5 speeds, v8 autos have 6 speeds, shifter to the right but not "bumped") and if you "bump" the shifter forwards or backwards, you'll see the big number pop up on your DIC, now you've ventured from Sport to Manual mode. It's good for pre-selecting a higher-revving (and thus more power) gear in preparation of passing someone or similar.
Sounds like you hit sport mode but then held one of the gears and took it to redline, not ideal.
There's a whole section on this in the owners manual, maybe that is good earmark reading for you to become more familiar.
Not fun to smell burning smells, be careful out there. If unable to shift manually, flip back to "D" mode or flip to "Sport" mode and do not bump it into Manual mode. Sport, as others have stated, is more aggressively shift-timed, and promotes a more exciting driving experience, if you're into that sorta thing.
V8 manual mode also features rev-matching downshifts... that's one of the best features of my car, I use it all the time. "Engine Braking"
2009.1 ZEPCOM MGM G8 GT
Kooks LT's, SOLO HFC & Mach Unbalanced with J-pipes, SLP Tips.
Livernois tune, VCM, FE3's, full Holden blue gauges conversion, iphone on display. Daily Driver FTW
The ZEPCOM G8 was SOLO's test mule
Bought 3/30/2009, retired 7/18/2017 at 136k miles, still strong. Been a great ride, she will be missed!