If my interpretation of 30 CFR is correct they have to over estimate the spill by four times the actual amount.
Hence the increase from 1500 to 5000 barrels per day of leakage.
Based on the subsea ROV photos the 1500 bbl seems a bit high.

Also note that there are many different estimates of the well leakage and the conversion between barrels and gallons varies from site to site.
1 API (American Petroleum Institute) barrel is 42 US gallons.

For example 1 gal of paint normally covers 350 square feet. (Industry average)