Just as a gut check to thermal capacity of the water: water has a heat capacity of 1 cal/gm-degC. 31.93 quarts of water at 8.34 lbs/gal is 66.6 lbs of water or 30,200 grams. Your mash tun is 10.8 lbs (4,900gms) at 0.3 cal/gm-degC and the grain is 10 lbs (4,500 gms) at 0.38 cal/gm-degC.

So your ambient equipment going from 72F (22C) to 154F (68C) would require: 4,900 * 0.3 * (68-22) + 4,500 * 0.38 * (68-22) = 67,600 + 78,700 = 146,300 cal

If the water was at 164F (72C) strike temperature it would contain: 30,200 * 1 * (73-68) = 151,000 cal.

Given a little heat loss and rounding error this is pretty close.

This again supports the observation that not having set your mash to account for the thermal rise of the equipment was your issue.