try this link. i believe you will find what you're looking for.
1/4-1/3 cup per gal.

Here is a link that might be useful: serenade max mixing rate

I think it might be a little more complicated than that. Assuming that your not trying to cover an entire acre you can figure how much per SQFT you need.

1AC = 43,560SQFT

At 3LB/AC (maximum allowed by the label) that works out to .0011OZ/SQFT (3LB=48OZ 48OZ/43,560SQFT=.0011OZ/SQFT)

You then need to calibrate your sprayer - figure how much solution you need to cover 1SQFT of crop. Fill your sprayer with water and spray a known square footage with just the water - for ease of math say 10 SQFT. Refill the sprayer from a marked container (like a big measuring cup) so you know exactly how much water you used. Multiply the area you need to cover by that amount divided by 10. That will tell you how much water you need in total. Take the total amount of water needed, multiply that by .0011 and that will tell you how many ounces to use in your patch. Mix that with the total amount of water needed and your good to go.

That's how they teach you to do this for your Applicator's License. That will give you the correct application rate. One of the problems using a handheld sprayer is it is very hard to keep your application even - people tend to use too much solution when compared to a mechanical sprayer (you can use your ground speed, nozzle size and operating PSI to accurately calculate your coverage rate pretty accurately). With a hand sprayer there is a lot of variation in the actual application. I think you could use the 1/4 to 1/3 C/GL mixture but I think in the end your going to over apply the product. Just something to keep in mind.

Tom

Here is a link that might be useful: Serenade MAX label