Hi
@Jayden2407 . Welcome to the forum, both you and your son.
Hypos, like everything else diabetes never have a rule book or rather its probably better to say they have various rule books.
Your son will learn the signs as to when his sugars are low and you will as well. It's always the time to go to the meter and get a reading BUT instinct should take priority if meter says anything below 6.
Scenario 1. Your son is watching TV , nice relaxed. His BS drops from 5.5 to 4 over the course of an hour. Chances are he'll be feeling not to bad, maybe only very slight hypo symptoms. Because his BS isn't falling rapidly the minimum carbs will suffice.
Scenario 2 . Your son is running around outside, burning more energy than his body can supply. His BS has dropped from 5.5 to 4 in the space of 10 mins and is still falling at a great rate. You've got to treat the impending hypo but also stop his sugars from continuing to crash, this scenario will undoubtedly require more treatment especially if you want to prevent a further hypo maybe an hour later.
Every hypo will have its own uniqueness about it. Experience, trial and error, success and failure will make you both great warriors regarding hypos.
Even the most long term T1's here still get caught out by them, myself included.
One thing I know for sure is that no one understands being hypo unless they actual go there. Non diabetics will give advice and rules but they have a limited amount of knowledge.
Your son in time will become the expert, listen to him, encourage him when it goes wrong and you'll all be fine.