Interesting. That's odd they'd do that. I think it's safe to say that it's not calibrated in the least. And, it will slowly change as your battery life winds down. My guess would be that by the time it gets to the second (last) bar that it's much less than half. I wouldn't stress it, you'll learn how to interpret the indicator through use.
I'm checking the diagram for your camera. The battery status should appear in the upper left corner of the rear LCD.
On a fully charged battery you should see a battery icon with three blocks inside. One is larger than the other two and should be the first to disappear as the battery drains. It appears to represent "roughly" half the battery power. The other two are smaller.
My bodies (I don't have a T4i) have 4 blocks inside the battery icon to "roughly" show each 25% of capacity.
Battery capacity is a bit like the fuel guage on a car (I live in Detroit and worked in the automotive industry for years). The engineers will tell you the ONLY requirement of a fuel guage is that if the tank is actually "full" then the fuel guage has to read full. If the tank is actually empty then the fuel guage MUST read empty (that's required). Everything in between is only an estimate.
If you're pushing it to the last block of power then you'd want to make sure you have a spare battery charged and ready to go. You might also want to invest in a battery grip (which holds two batteries). This not only doubles your capacity, but it also makes the camera a lot more comfortable to grip and repeats several key controls when shooting vertically.