For a pump up sprayer, you want to be closer to one cup of 12.5% per gallon of water or two cups of household bleach per gallon, and probably closer to 1/8 cup or less of simple cherry per gallon of water for siding.

For the composite, you need a stronger mix, and I would brush on instead of using a pump up sprayer for the composite decking. 1 gallon of 12.5% with 4 gallons of water and 1 cup of simple cherry in a 5er will be good on most composite. I prewet composite so the cleaning is more even, then brush and scrub from the 5er.