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.
Nate seems to be able to sense changes in the timeline or reality itself, as shown when he detected changes to the past, such as New York City being nuked by Nazis in 1942, causing World War II to last until 1947, and when the Legion of Doom changed reality using the Spear of Destiny, he was able to realise someone had "operated" on reality. However, this awareness still has its limits, as when Zari Tarazi's past was rewritten, Nate knew something was amiss but didn't know what it was, and eventually dismissed it.