Can you explain why for glyphosate Weedkiller there are two different application rates stated on the label depending on whether a sprayer or watering can is used?

A larger amount of water is required to apply the weedkiller through the watering can to ensure even and easy coverage of the designated area. A smaller volume of water is required to apply the weedkiller through the sprayer as they provide a better surface area coverage as finer droplets are created.