Some games feature achievements that give gamerscore in values not ending in 5 or 0, which can lead to an odd gamerscore total. Some players find the resulting gamerscore frustrating. Since its can indicated a incomplete achievement collection.
Developers may use odd gamerscore values to hint at a false ending, like in Borderlands DLC The Zombie Island of Dr. Ned, to fit in extra achievements, or to incentivize further game play by providing an odd point achievement early on with the corresponding achievement that sums to a multiple of 5 far later in the game. Perhaps as a reference to the stereotypically obsessive behavior of those who fret about the ending of their Gamerscore, some of these late-game odd achievements require collecting a certain number of unlockables or hidden items.
Not to be confused with zero point achievements.