Degree wheel, confused!

When using a degree wheel with 90 degree only. My first reading BTDC reads 44 degree and the second reading ATDC reads 79 degree. Here´s where I gets confused.
Do I ad 90 to the 79 readings to calculate the numbers where the cam is installed?
Any help is appreciated.
Just checking the cam install I did 8 years ago, he he. Not sure that I did this correct back then.
Thanks
Lenny