Factum in the sense you are using is a document which contains a brief summary of the facts, law and argument you are relying upon in support of your position on a motion or appeal. In your case, the facts contained in the factum should be in reference to evidence which is before the court on the motion usually in the form of an affidavit.
So, you have a motion which claims relief and is supported usually by sworn affidavit evidence. The "facts" section of the factum summarizes the evidence usually in a light favorable to your position. The remainder of the factum contains a summary of the law you are relying upon and your arguments as to why the relief in the motion should be granted based upon the laws and facts of the case (or if you are responding to the motion you will argue as to why the relief should not be granted.
I hope you ind the foregoing helpful, thanks.