NCL

Hi all, I'm new to the forum and I'd like to thank everyone in advance for any assistance they may give. I''m currently working as a reseach & design engineer for a capacitor manufacturer, but I'm fairly new to the job. I need some help with the thermal coefficient of unreinforced polybutylene terephthalate. The data sheet gives 2 ratings, 63 E-6/K (parallel) and 77 E-6k (normla) Does any know the difference between the two ratings? I would also like to know how to interpret this information. If I want to find out how much the material is going to expand at a certain temp, how do I use these figures. I've tried wikipedia but it's all a bit of a headache !! Anyone got an easy explanation? thanks in advance NCL