I am not sure what info or opinion you are looking for but the Fox Farm line is one of the oldest in the modern Cannabis growing world. And, they throw their support behind their products whether the user calls or eMails them.
The back of the bottles does show the dosage when no other nutrients are going to be used. It also shows the suggested reduced dosage if the grower is using the rest of the Fox Farm line or is using any other fertilizing program.
The products are strong so it is best to be careful and follow the companies suggested dose. The suggested measuring is in fractions of teaspoons and my thoughts are to get a set of teaspoons which includes the 1/4 and 1/2 teaspoon. Do that instead of grabbing a teaspoon from the silverware drawer. The products are dry and granular so be sure to measure to a leveling off of the teaspoon or 1/4 or half teaspoon. No heaping pile of fertilizer when measuring; level it off.
Another way to look at using these finishers is that there is a lot less room for overdose errors especially since the grower will be using them when the plant has entered into flowering. If a problem shows up while in the vegetating stage the grower can hold off putting his or her plants into flower till the issue is fixed; not as easy to do that once flowering starts.