What does the number in brackets after a command in the manpages mean?

Often, I read something like command time(1) or printf(3) in the manpages.

What do the numbers in the brackets stand for?

I believe you're referring to man pages.

The number refers to section of the manpages that the command is documented in. It's a historical Unixism. See man man.

To access different sections, you supply the number in the command, like :

man 1 time
man 7 time

Here are the man page sections:

   1   Executable programs or shell commands
   2   System calls (functions provided by the kernel)
   3   Library calls (functions within program libraries)
   4   Special files (usually found in /dev)
   5   File formats and conventions eg /etc/passwd
   6   Games
   7   Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
   8   System administration commands (usually only for root)
   9   Kernel routines [Non standard]