How to figure out your bulkhead?

[michika]

Originally Posted by Static

http://www.reefcentral.com/calc/drain.php

Show's what size pipe to use for your overflow. If you want to be super safe, then use 2 bulkheads for redundancy, or at least go a bit bigger than the minimum size recommended.

You are my hero! I spent an hour trying to google this with no luck!

So...
Using the following input parameters

Gallons per Hour = 2500
Drain and Overflow sizes are calculated as

Recommended minimum drain pipe diameter = 2.06 inches
Recommended minimum linear overflow size = 38 inches

So....what does linear overflow size mean?