IBM 5155 Manual To Operations page 29

There are normally three responses:
A An indication of the memory test
will
appear in the
upper-left comer of your screen. The number
should continue to increase until it equals the
amount of memory installed in your system.
Note: The Xs
will
equal the amount of memory
installed.
XXX KB OK
B One short beep should be heard.
Introduction 1-17