When Xiao Ming reported 666 numbers, 1-5 repeated 666/5= 133 times, and reported 1 again, so the sum was.

133*( 1+2+3+4+5)+ 1= 1996

Xiaohong's 1-7 was repeated 666/7=95 times, and reported 1 again, so the sum is 95 * (1+2+3+4+5+6+7) = 2661.

266 1- 1996=665

1996-665= 133 1