Plotting the curve is easy. You just plot concentration (x-axis) vs. instrument response (y-axis) and get the regression constants. The tricky part is figuring out how much to add.
What is the concentration of AN you expect in the rubber?
I do a lot of headspace SPME and I pretty much always calibrate in the matrix and I use the method of standard addition for calibration. There are lots of things you have to worry about when you're dealing with a matrix like rubber gloves.
If you know the concentration you expect, you might try adding 5X, 10X, 15X, etc. that amount directly to the glove material and see where you are. Simply adding it to the vial doesn't mean you're good to go. You have to equilibrate it into the matrix.
If adding 5X doesn't increase the response much (or at all) after equilibration, then for sure you need to add more. If it gets you out of the linear range of your detector, then you've added too much.
If you're a total newbie to headspace analysis, I would get a good textbook on it and get yourself a good understanding of how headspace analysis works and also the matrix dependence of headspace analysis.
I highly recommend:
"Static Headspace Gas Chromatography, Theory and Practice" by Ettre and Kolb.
I don't see it on Amazon.com but I do see it on Ebay. My copy was printed in 1997 but the information in it is all still valid. 1997 is the green cover. The older one is dark blue/purple. Again, all of the information in it will still be valid. Headspace analysis is a pretty mature field.
There are specific examples of how to determine styrene in pellets, vinyl chloride in pvc polymer, etc. You can use those mindsets to decide how to approach your problem.
Good luck.