Bitmasks are used to make a ton of booleans (true/false, or 1/0) exist in a single integer (number), in the expansion use case. (It has other advantages, too, but we'll focus just on this for your use case).
For bitmasks to work, they need to follow the power of two rule, meaning when bitmasks are being described, at a glance you can know if it will work or not if it follows a pattern like so:
1, 2, 4, 8, 16, 32, etc. <-- this is a power of 2 pattern.
1, 2, 3, 4,   5,   6, etc. <-- this is just incrementing by 1.
The expansions variables list is not using a bitmask, it's just incrementing by 1.
Doing a google search of "eqemu expansion bitmask" I found this post: 
http://www.eqemulator.org/forums/sho...89&postcount=3
With the info:
	Quote:
	
	
		| 0 - classic 1 - ruins of kunark
 2 - scars of velious
 4 - shadows of luclin
 8 - planes of power
 16 - legacy of ykesha
 32 - lost dungeons of norrath
 64 - gates of discord
 128 - omens of war
 256 - dragons of norrath
 512 - depths of darkhallow
 1024 - prophecy of ro
 2048 - serpent's spine
 4096 - the burried sea
 8192 - secrets of faydwer
 | 
	
 You simply add these numbers together to enable the expansions.
Let me know if this helps out!