Screenshots, system info, version info, comp details. It can only work this way, not based on vague descriptions.
As Mylenium says, we need a lot more info in order to help. Screenshots, especially.
Ok, I have provided some screenshots.
Here is what the project/comp looks like:
After I made the path (using the pen tool), I copied the mask path
Then, I pasted it into the null object position
In this next screen, you can see how different the keyframes appear. I want them to be identical.
Here is what the null object path looks like
Here is what the actual path should look like
You can download the project here:
You just want to copy and paste one keyframe from the mask path, not all of them.
First, do you have parenting applied to any of the layers? Is the layer containing the mask scaled?
If all you want to do is to copy a mask path and turn it into position keyframes try taking a look at this tutorial. The key is setting a keyframe first for the mask path, copying that keyframe, then setting a keyframe for position and then performing the paste. This tutorial is for a camera but it will work for any layer or property that has X and Y coordinates.