Nope. You cannot use only half of an A+B type nutrient. There are significant components missing. A main reason that those types of nutrients are packaged as A+B is that the components would chemically react if the two were mixed without being diluted first.
The instructions for 200L res sure sounds like a commercial hydro nute... and that means that if there is any pH buffer added, it is going to come out at the wrong pH (too acidic) for your soil garden. Assuming you are in soil?