interpolation search question

I have a bit of code from a textbook I am looking to understand for interpolation search, it says:

next= low + |(x-a[low]/a[high]-a[low])*(high-low-1)|

the | are ceiling.

I understand what it does in finding the estimated location based on the percentage given by the division, I was just wondering why low is added to it after an estimated point is found, it doesnt even specify what low is in the text. Thanks for any help you can give me. :D

How does this question relate to the java programming language?
It appears to be an academic computer science topic.
Have you tried google?

Oh sorry, am I in the wrong place for such questions? I have tried google but the question is kind of a strange one as its just the one added variable I dont understand, I was hoping someone had used something similar.