@kutsyy, wow, your emitters are dumping some water! Do you know the total square footage of the area the bubblers waters? At 1 GPM, I'd assume there's some surface accumulation that spreads before the soil absorbs it all.
Correct, we max precipitation rates at 20 in/hour. However, if the square footage of the bubbler coverage is changed from 1 square foot to 10 square feet, then the PR is only 19.25.
Here's a spreadsheet that makes the math easy
Hope this helps. Are the bubblers adjustable? If so, they usually "click" as you turn them and you could figure out how many clicks they are closed. i.e. 10 clicks to close, but set to 5 clicks from max = 50%, therefore your GPM is only .5 GPM