It really depends on your level and stuff. For NEW grammar points (that you aren’t familiar with or haven’t really encountered enough yet) it is A LOT. If it’s just a sort of review (let’s say you are N3 for example, N5 would be EASY at 6 grammar points per day, N4 would be quite manageable, N3 would become difficult, and adding grammar above your level would be my personal concept of hell )
It’s mostly because you need time to internalize the grammar, potentially read up on it from multiple sources to gain a deeper understanding and have the chance to encounter it in the wild (or targeted look-ups).
But as I said, mostly depends on your actual level. And it’s always do-able, but you might get low accuracy on reviews, and if you have ghosts enabled on the strictest setting (which I personally recommend, but that’s up to you), the number of reviews can quickly spiral out of control.
For example, I consider myself very familiar with N5 grammar, but reset on the 16th for a strict, no typos and able to think of all alternatives run through. It still took me up to today to run through all N5 grammar points, as I didn’t want to overwhelm myself. So that would be like 4 - 5 grammar points per day roughly.