https://stackoverflow.com/questions/14338355
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Partial body lengths are pretty well explained by this tumblr post. OpenPGP messages are composed of packets of a given length. Sometimes for large outputs (or in the case of packets from GnuPG, short messages), there will be partial body lengths that specify that another header will show up that tell the reader to continue reading From the post:
A partial body length tells the parser: “I know there are at least N more bytes in this packet. After N more bytes, there will be another header to tell if how many more bytes to read.” The idea being, I guess, that you can encrypt a stream of data as it comes in without having to know when it ends. Maybe you are PGP encrypting a speech, or some off-the-air TV. I don’t know. It can be infinite length — you can just keep throwing more partial body length headers in there, each one can handle up to a gigabyte in length. Every gigabyte it informs the parser: “yeah, there’s more coming!”
So in the case of your screenshot, pgpdump reads 8192 bytes, then encounters another header that says to read another 2048 bytes. after that 2k bytes, it hits another header for 1037 bytes, so on and so forth until the last continue header. 489 bytes after that is the end of the message
The 1022 bits, is the length of the public modulus. It is always going to be close to 1024 (if you have a 1024-bit key) but it can end up being slightly shorter than that given the initial selection of the RSA parameters. They are still called "1024-bit keys" though, even though they are slightly shorter than that.
