At about that size and age there is a standard dose. Pedi titrates up but adults are standard. People do tend to get to know how they are feeling and if they have additional stress coming up some adjust their dosages.
The best way to know the amount is to go to the CVSA web page and under the research tab, click on the Supplement Study. The doesages are in that study. Start lower, increase slowly with doctor approval. Quality of the supplements could make a difference. Carnivore can be prescribed, CoQ10 from Epic4Health and Healthy Origins is pharmaceutical grade and therefore the dosage per capsule should be consistent. If you might be increasing the dosage, be sure that there nothing like Vitamin E in the capsule. While you might be able to increase the CoQ10, you don't want to overdose on the other components. Healthy Origins suspends in olive oil Epic carries the brand that is usually used in controlled studies. Both will offer discounts (call to let them know this is for CVS) and I think a chemist will still get on the phone to answer questions.
Dr. Boles felt that adding vitamin B or riboflavin after being established on CoQ10 can be very helpful. Some do add in Magnesium. Watch for the type of Magnesium as it can be laxative. Some prefer a chelated product for that reason.
Good luck, hope the supplements help this time around.