need opinons on ignition timing problem

[Tom N]

I was checking to make sure my igntion timing was set properly today and found it not to be. problem is when I remove the tps and stab the gas a few time and get it into timing mode it will idle about 900 rpms which is close enough but to get it to 15 degrees i have to turn the cas all the way clockwise. I cant even adjust it to more than 15-16 degrees.

I double checked timing marks and they seem correct when at tdc. Any ideas why I have to turn the cas all the way to the right to get 15 degrees.

Edit to add motor is a S15 sr20det