At this point in time you should be testing every other day. You put in Dose #2. yo should then jeave skipped testimg the next day and tested the day after that. I f you got 0 on that ammonia test, that would have been your first of the two tests at that level. You would not be testing the next day but would the day after that. This would have been your 2nd consecutive test of 0 ammonia which singals the time to do the snack dose.
This means you:
Added Dose #2 on day 1
did nothing day 2
tested day 3
did nothing day 4
tested day 5
That means the soonest one can add the snack dose after Dose #2 would be 4 days later. For some it may be 6 days. Since you got 0 for ammonia the first test, you should also get 0 for the second because no more ammonia has gone in. But you need to wait that long to allow the nitrite bacs to multiply without being overwhelmed by too much nitrite which will slow or reverse a cycle.
Your next move after the snack dose will not occur until nitrite has come back down below 1 ppm.