I don't know anything about the GHL system, but if the doser isn't designed (or you can disable the feature) to "catch up" if there's a power outage, you could put it on a timer. So, you could set it to dose some amount greater than 8.3 ml/day, but put the doser on a cheap plug in timer that leave it on all day, but shuts off for X minutes. If you're lucky, you can find the combination of total dosage per day and skipped doses to work out to 8.35ml/day.
Another option might be to add some water to your tank. If you have space to add a few gallons, that would essentially dilute the dosage.
Of course it's probably easiest to just 'deal' with it until the demand changes up or down a little bit so that 8.3 or 8.4 work for you.