Understanding buffer/bitrate statistics in Media Player Classic

I understand that the two numbers under bitrate are the average bitrate and the current bitrate of each stream.

But what are the two numbers under buffers? I suppose the second one is the amount of data loaded in memory, but what is the first number? The amount of data decoded?

Also, why are there a jitter and a sync offset?

(For your reference, here stream 0-6 are video track 1, audio track 1-2 and subtitle track 1-4.)