Apple

I use the iPhone mail app for my primary emails and today I’ve been having an issue where it will show I have 1 less unread email than I actually do. Like right now I have 4 emails unread but then it will show only the number 3 on the app icon and then it will change and then will show 4 again and it keeps going back and forth. It did it to me earlier in the day when I had 75 emails but the app icon kept only showing 73 or 74. Anyone else having this problem? Is it a bug?