I'm using gvim version 7.4.205 for Windows, if that matters.
If I type
:help :bp, it shows the help for
:[N]bN[ext][!] [N] *:bN* *:bNext* *:bp* *:bprevious* *E88* :[N]bp[revious][!] [N] Go to [N]th previous buffer in buffer list. [N] defaults to one. Wraps around the start of the buffer list. See |:buffer-!| for [!] and 'switchbuf'.
*E88* in the top right of the entry?