For my mixed reef - 6 times a day it gets dosed 2 mL (every 2 hours, as I do not dose after lights out)
For my fish barn setup (about 500 gallons) - 8 times a day it gets dosed 5 mL (every 3 hours)
For dose per gallon and how many times per day, that is kind of hard to come up. You have to know how much is consumed by your tank in a given time and make sure not to get anywhere near an unsafe level for fish. This also changes from day to day, so you need to find a happy medium. I aim for .1 ppm or so and watched my fish like a hawk when I first started dosing to the mixed reef setup.
I also used a Seneye, to begin with. But have since sold it and just keep the dosing the same, except when I go out of town for long periods of time. I then shut down that doser, just as a precaution.
But for the amount and how I do it, Austins ammonia (what I use) will raise ammonia about .1 ppm for every drop added to 6.25 gallons.. This means that 1 mL will take 125 to .1 ppm of ammonia. This level does not shift a seachem badge from "Safe" color and on a clean/new slide from Seneye, registered .08 to .12 ppm of ammonia.