Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
1) m+n<0 - m and n can both be negative numbers and still satisfy the equation, or either m or n can be negative and the other positive and the equation will still be satisfied. Thus, InSuff.
2)The only way you could get mn <0 is if one of those numbers is a negative. If both are negative, then multiplied together, they'll be greater than zero.