Mod

Modular Math Operator. BINARY

Removes two values from the stack. Performs modular arithmetic on the two values, placing the result onto the stack.

351 69 mod

is the same as (351 mod 69), which is 6. Thus "351 69 mod" is equivelant to writing "6".

Mod allows a user to check whenever a given value is a multiple of a specific number. Ie.

cond
*.robage 5 mod 0 =
start
'do something every 5 cy's
stop

This particular code allows a bot to essentially set an action to activate every 5 cy's.