On the IDS form itself, you can check either of the two boxes to provide your certification statement. In the first box you are essentially stating that you filed the same patent application in one or more foreign countries, and when foreign patent offices conducted their own patent search, they informed you about the reference you are now submitting to the USPTO in the current IDS, and that your current IDS submission is occurring not more than three months after being informed of the reference by the foreign patent office. In the second box you are essentially stating that you weren't informed of this reference by a foreign patent office, and that no more than three months have passed since you first discovered the reference you are now submitting in the IDS.