Question about natural family planning.

I feel really dumb but I can't find a direct answer on Google 😓 I'm new to this app and natural family planning. When the app started it asked what our preferred birth control method is, I said withdrawal. We have 3 kids (1girl and 2 boys)(not using withdrawal and unsure if we wanna try for a girl. On days the app says low chance of pregnancy, is it calculating withdrawal method or if he cums inside??? I miss it(him cumming inside) honestly but with 2 boys under 2....uhhh we need to wait a bit! We have been using withdrawal with NFP for 8 months and it's been working so far! I love it so far!! ❤️❤️❤️

B4 any Karen's come at me...(jk, I kid) I can't do birth control, I'm horrible at remembering, plus the pills and iud gave me horrible side effects. The ring never stays up, ever! Even with doctor placement. And we're in our 30s and over condoms(I know age doesn't matter). So please, you don't need to educate me on our other options. I just need clear answers on NFP. 🥺 💗