I think that reading the source is perhaps the quickest way to see what is going on so you can get something done. But when it comes to designing software, it is a good idea to have a spec to design to, rather than just the code, because the spec may provide the intention of the code, whereas the code itself is providing the implementation, which is more likely to change (one would hope, anyway). If there is a difference, it's best to try to submit a bug report or tech support request of some sort, if this is possible, to clarify things. But, in the end, the code needs to work, so it's best to read both and try to figure out which side is right.