If your total profit is $1000 on your account, one of the previous days can't exceed $300 (30% of $1000 = $300), but if it does, no worries, you need to increase your total profit. For example, if you make $330 on your best day, you just need to increase your total profit from $1,000 to $1,100 and you enter the consistency rule (30% of $1,100 = $330).
In one day, you can't calculate your consistency rule because in one day you reach 100% of total profit.
The minimum calculation period is 4 days. For example, if you make $1,000 in 4 days ($250 each day), your best profit day is $250, and $250 out of $1,000 total profit represents 25%.
But if, out of those 4 days, you have one day at $350, one day at $100 and two other days at $250, it's still $1,000. HOWEVER, your best profit day is $350. A day at $350 out of $1,000 total profit exceeds 30% of total profit ($350 out of $1,000 represents 35%).
The consistency calculation is a tool for objectively assessing a trader's performance by determining whether he is consistent in his earnings. For example, if you have 400 trading days (this is an assumption), your consistency could be very low due to the high number of trading days. A large gain won't greatly affect the value of constancy. On the other hand, for a trader with only 2 or 3 trading days, a lucky day will have a significant impact on his future performance, as he'll need to make more profits over the long term to maintain 30% consistency.
Consistency is therefore calculated on a day-by-day basis. Similarly, for a loss, the more you have big gains followed by big losses, the more this will impact the gain needed to stay within the 30% constancy. However, this neither affects nor increases the value of constancy at any given moment.