According to the prescribing information sheet:
The recommended minimum dosage is 2.7 mg selamectin per pound (6 mg/kg) of body weight and 0.45 mg sarolaner per pound (1 mg/kg) of body weight.
Administer the entire contents of a single tube (or two tubes in combination for cats weighing over 22 pounds) of REVOLUTION PLUS topically in accordance with the ...
This post is several years old but I will update it to add that there is now Revolution Plus which includes an additional active ingredient specifically targeting ticks. This might already be common knowledge to many or most pet people but hopefully will help anyone searching this information.