Here are all the levels with descriptions:

Very Low level: Weak/Average/Strong [VLL-W / A / S]
This is the lowest level of Reiatsu. Mostly people that have just begun spiritual training.

Low level: Weak/Average/Strong [LL-W / A / S]
At this level the Reiatsu of your character has already developed itself to a Reasonable level, Your character is able to use Kidou and control their Reiatsu, your character will be able to use their special abilities better if they have any.

Middle Level: Weak/Average/Strong [ML-W / A / S]
This will be the most commonly seen Level, it's the average.

High level: Weak/Average/Strong [HL-W / A / S]
This is commonly known as the Captain level, this is a strong level that only strong characters will be graded with.

Very High level: Weak/Average/Strong [VHL-W / A / S]
A rank that is held for those who are truly gifted

Here are the characters with there Teir level applyed.