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.
^ pulls up to true shikai ichigo and ichigo appears intimidated by grimmjow, this would mean they're comparable in power level, meaning resurreccion grimmjow would likely be relative to True bankai ichigo (without the horn of salvation)
^ One shots askin nakk le varr in his volstandig who's a high tier sternritter
^ askin was able to beat true shikai ichigo, showing how resurreccion grimmjow would be > true shikai ichigo
^ True shikai ichigo could cut the soul king
^ true shikai ichigo is equal to mugetsu ichigo since its the power that he used to defeat sosuke aizen in their fight which is mugetsu