Missing reps in workings

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If while doing a mantra related to a 40 days working, let’s say the reps for the day is 30,if i reach 20 and i receive a call i should answer or similar, or just for some reason miscount the reps.

Should i just do the 30 reps again from scratch again in that day. Or the whole working is ruined and i should start from day 1?