about float

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    float j = 1.0f, i =j;
    int n = 0;
    for(; i - j - 1.00f; ++n, j /= 10)
    {
        ;
    }
    printf("%d", n);

    return EXIT_SUCCESS;
}

I supposed the output was 6, because the float's precision is 6, but
as the result, the output is 20.
why?