Hal Abelson contributed by holding this report hostage

what did he mean by this?

at the end of: https://www.cs.indiana.edu/scheme-repository/R4RS/r4rs_12.html

>>1
Don't question the dark lord's macro knowledge.

>>2
Why not?

>>1
Did you know that Hal Abelson is a Jew?

>>4
Did Jews know that Hal is Abelson?

Go to the previous, next section.

It means that you can go to the next or previous section.
But don't be ashamed, technical documentation can be a challenge for many, you have to switch between informal language and formal language. In this case you mistook a piece of informal language for a formal specification.