Every lobby has a favourite percentage. 99.5. 99.6. 99.8. The number is always printed larger than the rule that produced it. I stopped believing RTP tiles the year I found two tables with the same badge and different naturals.
A return figure without a derivation is a colour.
What I want under the badge
Three things, in writing.
The rule set: decks, natural, soft 17, peek, double, split, surrender. The source: help panel, not a blog memory. The arithmetic: how you got from those rules to the percentage, and whether any rebate is already folded in.
If a rebate is folded in, say so twice. A 99.78% "effective" return that includes rakeback is not the same object as a 99.78% table RTP. Mixing them is how marketing eats analysis.
Two honest numbers beat one heroic one
I would rather see a game disclose 99.44% and an independent pricing of the same sheet come in a few hundredths lower than see a round 99.9 with no recipe. Agreement to the hundredth is suspicious. Agreement to the neighbourhood, with the gap explained, is how adults talk.
Rakeback then gets its own line: percent of what, credited how, withdrawable or not. Effective return = 1 − (edge × (1 − rebate)), and only if the rebate is really a rebate.
A page that bothers to show the sums
Duel Blackjack Pays is the example I keep because it does the unfashionable thing. It prints the live help-panel rules, prices them separately from the game's own RTP line, then applies the advertised 60% instant rakeback to both: 99.44% becoming 99.78%, and their 99.3943% becoming 99.76%. You can disagree with a step. You cannot say the steps are missing.
That is the standard I now use on every other site. No working, no headline. I will sit a slightly worse table that tells the truth before I sit a miracle that will not show its homework.
One more filter: if the headline RTP changes when you toggle a language pack or a "fun" mode, you are not looking at a table constant. You are looking at a CMS. I want the same percentage in the help panel that I want in the review. If they disagree, I believe the panel and I discount the review.
Do not average two RTPs to be polite. Fights between numbers are information. Averaging is how you lose the fight.