The result lives in your analytics panel rather than on the post, so screenshots of the same date range are the method.
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Unlike a public counter, this figure lives inside the analytics panel of the page rather than on the post. That has two consequences for a sample. The first is that verification requires access to the panel rather than a signed out browser. The second is that nobody except you can see the result, which is worth deciding how you feel about before you spend anything larger.
Reporting in that panel is also aggregated over a period, so a small addition often takes a day or more to appear and may then sit inside ordinary movement. Patience is part of the method here rather than an inconvenience.
Take a screenshot of the relevant figure before ordering, with the date range visible, and take another with the same range afterwards. Comparing two different ranges is the most common way people convince themselves that nothing happened when something did.
Short answers to what people ask most before ordering.