The property listing doesn't mention the flow rate on the well. I checked to see if there was a matching well start card in the state's database of well logs, but couldn't find any definite matches. This is all historical information anyway, and is not necessarily a reflection of a well's flow rate today.
The closest possible match I could find in the state's database was a well log from 1977 for an Edwin Danielson with only a Route & Box No. given for an address. Tax records show the property for sale being owned by a "Danielson" estate. For what it's worth, that well log showed a yield on the well at the time it was drilled as 12.0 gpm. (Again, this may not be the same property and well as that for the property for sale.)
The best way to find the flow rate of a well on a property you want to buy is to find the property you really want, then enter into a contract to purchase it with a contingency to have the well tested. Then, hire an independent testing company to do a flow test for you. While the results are not a guarantee that a well will produce the same flow forever, they are the most reliable measure of what a well is producing today.
Prices for a flow test vary by company, but an average range would probably be about $200-$300 for a flow test. However, an independent, professional tester will be more likely than a home's seller to do a reliable, accurate job of measuring the flow rate (which requires equipment most home owners don't have). And a professional well tester can draw samples for other tests while he's there (e.g., arsenic, VOCs, pH, etc.).
For less cost, you also can search historical well data for other properties in the general area (see link below). Keep in mind that this is just history, and not an indication of what a given well will do today--especially if that well isn't even on the same property.
I hope this was helpful.
Best of luck,