to explain, basically each stat category is an aspect of your character, that much is self explanatory, but this system exists to provide a guideline for who can outrun, outthink others in a contest of that atribute. A genin with primary strength could lift as much as a chunin with secondary. A chunin with primary speed might run as fast as a Jonin with secondary speed, ect. The categories themselves can also be given a primary secondary tertiary, but this is optional.
Example stats
Physical
Strength: Secondary
Speed: Primary
Defense: Tertiary
Mental
Intelligence: Tertiary
Tactics: Primary
Will power: Secondary
Chakra
Power: Tertiary
Control: Primary
Reserves: Secondary
AND
Physical Primary
Strength: Primary
Speed: Tertiary
Defense: Secondary
Mental Tertiary
Intelligence: Tertiary
Tactics: Secondary
Will power: Primary
Chakra Secondary
Power: Primary
Control: Tertiary
Reserves: Secondary
here is a guide for what each stat catigory might be used for
Physical (Taijutsu, Physical fighting, ect)
Strength: Lifting, striking, throwing, swinging weapons
Speed: Running, jumping, balance, reflexes
Defense: Blocking, how much "health" your character has/damage they can take
Mental (Genjutsu, strategy, forming ideas)
Intelligence: how well educated your character is, how much background knowledge they have to work with
Tactics: How complex a plan your character can come up with or see through, traps, strategies ect
Will power: Resisting trauma, breaking genjutsu (where aplicable), pursuit of endeavors in the face of adversity
Chakra (ninjutsu, casting chakra based techniques, ect)
Power: the effectiveness of ninjutsu, how hot a fire users blasts are, ect
Control: Using Genjutsu, Puppetry, any chakra based manipulation
Reserves: Think of this as your characters chakra bar, how much total chakra your character has to work with