elementary number theory - Modulus Function

I am watching a tutorial an i saw how to use the modulus they said if 20/7 = 2.8571422857 you must subtract the whole number then multiply it by the divisor

now am trying to understand a Public key encryption example this person said 595^611 mod 899 = 119

i cant see how he got the 119 which is w

is video is http://www.youtube.com/watch?v=FxwmpsRCuqQ

what i did was take 611 divide it by 899 then i got 611 when i raise 585 to 611 as in 595^611 i got math error on my calculator please any one can you assist me how he got to that number are is he wrong? oh if u illustrating cann u use umber that can be process by calculator