You should start counting all the hours since your last bite food (green chilies w/salt in your case).
You can expect day 2 to be the worst, but by worst I mean still not that bad since a 3 day fast is not terribly difficult.
Good luck!
For your first fast, for sure count today. A few chillies aren’t going to do a whole lot, except make you more hungry. Coffee and tea will help. Plain is best.
Electrolytes will help you, but you won’t likely run out in 3 days. You have 4-5 days circulating at all times. There’s a million FAQs around to make some, or find some on Amazon.
In general, one of the days will be worse. Some people find the first the hardest, some the second, the rest the third day. You will just have to find out.
Good luck.