The function numbers are what they are named when they get decompiled. As we do not have access to the unobfuscated minecraft source, we have to decompile and deobfuscate it ourselfs.
That is what the tools the MCP Team provides is doing. By using their system, we (the modders) can submit understandable "real" names to methods.
In every major minecraft update it is changed up a lot and therefore a lot of the names must be re-added or completely re-done as methods change etc.
Therefore when the new versions are just comming out, we (the modders) haven't had time to mess around to much with the new code and submit names, therefore a lot of things will have such names for the time being.
Also keep in mind that Forge is NOT out with a stable release for 1.7.2 it's still very much indev, and so is MCP.
Therefore I would NOT recommend starting to learn modding by starting for 1.7.2 now, I would either wait 1 month and spend the time learning more Java and computer science or whatever.
And come back once things are a bit more beginner friendly.
Either that or start for 1.6.4 and re-learn some of it when things are more settled for 1.7.2