I'm thinking it's probably not an on-off condition.
Probably a fixed, continuously draining amount from the DC balance, and whenever the DC is empty, the SR starts increasing at a rate of 5% daily, spread continuously throughout the day.
In which case, if you add 1 DC, it likely means that the SR stops increasing for a few minutes until the 1 DC balance is drained and then SR starts increasing again until the next time someone adds DC...