Hi James,
It all depends on the size of the bubbles and the size of the tank!
If you've got a drop checker with 4dkH water in there with the pH indicator, then you'll know if there's enough co2 in the water column.
If would suggest you start of slow, maybe 1bps per second and observe the drop checker a few hours later (as the change isn't instant). You want the drop checker to be green, yellow is too much turn it down and blue means there's not enough in there.
Just be patient and take your time to get the right co2 in there.