calvingloster:
I can't understand this? Why do they say u can use the LM317 as a voltage regulator. It's ridiculous
Because it is a voltage regulator 
Have a glance at the datasheet. 240? is the usual value for R1. (What would ever possess a person to use 5?.) The LM317 develops a 1.25V reference voltage across R1, resulting in 65mW power dissipation. Use 2400? for R2, this will set the output voltage to 13.87V, and 66mW dissipated by R2. Where is the problem.
Use 1% resistors and change R2 to 2370?, this will come closer to the target voltage, 13.71?.