That number is about what I expected.
The Chiefs are 2-0 and the 49ers are 0-2 so some might think it's a little high but looking at how each team has played it's hard to predict this one. The Chiefs are relying on defensive and special teams touchdowns which are nearly impossible to predict. The 49ers meanwhile were stomped by Seattle while the Saints barely squeaked by them.
The reasons the Chiefs can win include: Running game, strong overall defense and home field advantage.
The reasons the 49ers can win include: Frank Gore, strong pass rush and they are (probably) a more talented team.
This will be the third consecutive game the Chiefs will enter as an underdog. Think about this: The Chiefs could be 3-0 heading into their next game against Indianapolis, where they'll surely be an underdog. The week after that, they'll play Houston, where they're almost sure to be an underdog again.
The Chiefs could go undefeated and not be favored to win a game until Week 7 against Jacksonville.