Ok, my bad ..i didn't mean 20 mins including doing the truss rod - you have to let it settle.
I'd say do not start adjusting the truss rod yourself just yet, not on a brand new guitar .If you have high heat/dryness/humidity then ,yes, it may need adjusting after a short while, which your does- but- I still favour the fact that the shop is in the wrong, it would be worth it to take it back to the shop. i'm sorry i don't know your guitar model it may be an allen key adjust or may need a special wrench/driver ..in which case you may have to travel to get the tools, anyway.
You can snap a rod fairly easilly and ruin your guitar i only started doing this kind of work on a really cheap old 6 string and very carefully worked my way up, i've only done about 10 or so guitar's rods - and had no problems, except that cheap guitar has a hex nut that was partially rounded in the factory,[still adjusts],but all my guitars had some age on them before i started this, so pracice very gently on a beater before you start playing with 7 string exotica.
The more complex a guitar is the more complex things can go wrong..once you've adjusted the neck,everything else usually needs to be tinkered with as well.
I know it'll be a drag waiting,but, you should save yourself major ...sheeet doing it this way, no offence to your technical skills, but, even if you have all the info on a (model of) guitar it still takes figuring out to get an individual instrument right.
Accuracy,you say? hmm interesting concept..