0 all around is ideal, but i find mine will typically be -1 or so. just make sure you top off the tank, select full tank when doign the recal, and make sure there arent any codes being thrown before doing it. also make sure to put it in ET mode before starting the recal (with truck on on flat ground, shift to neutral, select manual mode, click ok when the warning pops up on the dash, then turn the vehicle off without putting your foot on the brake. then turn the truck to accessory power with your foot off the brake, then floor the gas pedal 3 times in a row. if you've done it properly you'll see an ET pop up on the screen in the lower right corner of the dash. then go about your forscanning
ETA: if you do the recal outside of ET mode or with a code, your recal results will read something funny like zeros in the front and +6 in the rear. the key is having the measurements being about equal on truly flat ground... which is surprisingly difficult to find where i live