Now I have problems. Not major of course....I'm a sharp guy

.
I just got used to "SOI Delay" in my old definitions.
Now with the new definitions I have "SOI Offset".
The "SOI offset" is 1/2 of the "SOI Delay".
I have already made an "SOI Delay" calculator.
Why the change?
It's not a big deal, I have since altered my calculator to work with the "SOI offset" of the new definitions but I was just curious of why and how.
Thanks!!