I'm not a big proponent of small sample sizes, but you can absolutely have a good zero with three rounds if you're a decent shot and have good equipment.
Below are seven 3-round groups........using factory ammo........shot on different days.........and the suppressor was removed and reattached in between groups.....
7-15-2021 - 0.328 MOA
View attachment 343215
8-4-2021 - 0.241 MOA
View attachment 343216
8-6-2021 - 0.577 MOA
View attachment 343217
8-10-2021 - 0.312 MOA
View attachment 343218
8-10-2021 (2) - 0.416 MOA
View attachment 343219
8-12-2021 - 0.357 MOA
View attachment 343220
8-17-2021 - 0.499 MOA
View attachment 343221
Aggregate & Breakdown:
View attachment 343223
View attachment 343226
21-shot aggregate is about 3/4 MOA, and the difference in dope at 1,000 yards tells the tale. I've shot a single round after remounting that scope, adjusted, and had a good zero with that set-up on more than one occasion. Again, I'm not saying everyone can/should use 3-round groups. If you have one of these set-ups that's 1.5 - 2.0 MOA for 10-round groups, then yeah, you better use more than 3. I'm just saying it's completely doable for some.
To the OP, I think a single box is pretty worthless unless you are keeping shots pretty close. If you have unknowns (shooter, ammo, scope, rifle, etc) you will want way more than a few rounds.