Here is the outcome.
I stopped by NPD to show them the hose was too large for 5/16" fuel line. Told the salesperson I installed a short section and it leaked. He promptly measured the hose I.D and said "it is 5/16" so nothing is wrong. He went and got another hose kit and measured the hose I.D. and said "it is 5/16".
I said, " here is a piece of hose I bought for 5/16' tubing and it fits perfectly." He measured my piece of hose and said,"it is a 1/4" I.D., it is miss marked. No matter how hard I tried to convince him that the Marti hose was too big he would not relent. I told him this hose is useless to me for may application I want to return it. Since I had cut off a short section, he would not take it back. Could be my last purchase from NPD.
My understanding has been a hose for a specific size tube has a smaller I.D. than the tube so it can seal better. Maybe I am wrong, but logic tells me something different.