The only way to rudimentary way to know how much of the dose of E is doing anything is through various blood tests. And they do not tell the whole story either. Many in my group have been through shots, pills, patches, EV, and premarin. All with varying results and some side effects. Eventually settling in on something that worked for them. I've also seen in various discussion threads on doseages and E levels how some endos start at XX and just rely on the end physical results to primarily guide them. Others use somewhat arbitrarily set E levels as the absolute authority.
I've been on premarin, EV pills, and shots and patches. As a results driven engineer I've found that shots work the best. Even there the manufacturer seems to also matter.