The Superhero Database Classification number, or SHDB Class, is a number that represents the overall 'power' of a character. All traits of a character are used for calculating the Classification.
What it DOESN'T mean
This doesn't mean that a higher class would always beat a lower class character. But the bigger the difference in Class is, the more obvious it is who'll win in a fight.
How is this calculated
( INT^1.3 + (STR*0.5 )^2 + (SPE*0.5)^2 + DUR^1.6 + (POW + (SPS*SPL))^2 + COM^1.8 ) ^ TIER
Super Power Score and Level
Every Super Power has a score (SPS) that is used to calculate the Class. Each Super Power also has 3 levels (SPL). The level is set when connecting that Super Power to a character. The level determines the final score, of the Super Power, being used in the calculation.
Now I know you don't care about scaling properly, and that you're just biased against SCP for no reason
They've got a space time corridor where there is no concept of space and time.
There are parallel universes called e.g. the Tau System which can be completely merged with Chaos / Pharaoh 90 and then move through interdimensional space right on a doombringing collision course with the primary reality where most of the story takes place.
Alternate dimensions like Elysion exist aplenty, even "only" Sailor Mercury can already casually + literally create Superdimensional Space already in the first story arc:
Now add to all that plenty of time travel (Chibiusa from a possible future, Sailor Cosmos likely also from the future, it's possible to travel "anywhere" and "anywhen" with a spacetime key anyways. On top of that there's a parallel universe which exists behind mirrors, which duplicates everything we've summarized so far but in a "dark" way because it was possessed by yet another incarnation of Chaos / Nehellenia.
And we still aren't even in the final story arc, where finally all of this is explained as created only by so-called Star Seeds (== Platonic Concepts which define what can exist at all) in a primordial sea (called the galactic cauldron), all of which Sailor Moon / Sailor Cosmos can blow up and also restore (with Lambda Powers).
Sailor Moon is a pretty powerful verse, and I've seen A LOT of people who scale Sailor Moon to Outerversal or more. At least that's what most people who actually know the verse would scale them too.