13 lbs of Cal-Hypo last night??? Hope that is a mistype.
@JamesW is the pro - so if he says to do the SLAM, do it and not worry about ammonia.
Off to Ocean State for you today, to buy several cases of Liquid CL.
808 E Street Rd, Warminster, PA 18974
Your CH should have increased by about 40 in about the last day due to the Cal-Hypo (assuming the 13 was really 3). Still fine now, but need to stop it or by the end of the SLAM you could be in a bad spot. Then the only option is to partially drain the pool. As noted, the slower dissolve/incorporation will always keep you behind the curve in hitting your SLAM targets.
Retest your CYA, but bring the sample inside and let it warm up first. It can be affected by cooler water. Your pool isn't all that cold, so it may not change, but good to verify.