DPS stands for Damage Per Second, and is used to express the damage that a defensive tower does in one second. That kind of information is given in the actual Backyard Monsters game. The purpose for this information is to compare the relative strength of one tower to another, and is the information usually presented by Kixeye within the game when the statistics of the tower are presented during the upgrade process. The information here isn't intended to be misleading, but is being used to show how effective it would be to upgrade one tower on your base instead of another one.
Howerever, DPS is NOT the actual damage the tower does to an attacking monster. The actual damage is called DPShot, and that is the real damage dealt to the attacking monster.