How to pass display number to xvfb-run?

I tried to start chrome with xvfb-run: - Ubuntu 18.04.5 LTS - Chromium 105.0.5173.0 If I specified display number as 76, xvfb-run failed to start:

$ xvfb-run --error-file=/tmp/Xvfb-errors.log -s ":76 -auth /tmp/xvfb.auth -ac -screen 0 1920x1080x24" chrome >./chrome.log 2>&1 &

$ 
+  Exit 1                  xvfb-run -s ":76 -auth /tmp/xvfb.auth -ac -screen 0 1920x1080x24" chrome > ./chrome.log 2>&1

$ cat chrome.log
[25736:25736:0819/203148.686095:ERROR:ozone_platform_x11.cc(246)] Missing X server or $DISPLAY
[25736:25736:0819/203148.686137:ERROR:env.cc(226)] The platform failed to initialize.  Exiting.

A check showed that /tmp/Xvfb-errors.log was empty. If I specified display number as 99, xvfb-run succeeded. And :99 :99 was passed to xvfb:

$ xvfb-run -s ":99 -auth /tmp/xvfb.auth -ac -screen 0 1920x1080x24" chrome >./chrome.log 2>&1 &

$ ps -ef | ag xv
rb_user  25836 25820  0 20:32 pts/0    00:00:00 /bin/sh /usr/bin/xvfb-run -s :99 -auth /tmp/xvfb.auth -ac -screen 0 1920x1080x24 chrome
rb_user  25847 25836  0 20:32 pts/0    00:00:00 Xvfb :99 :99 -auth /tmp/xvfb.auth -ac -screen 0 1920x1080x24 -nolisten tcp -auth /tmp/xvfb-run.FWVOd6/Xauthority

$ xdpyinfo -display :99
name of display:    :99
version number:    11.0
vendor string:    The X.Org Foundation
vendor release number:    11906000
X.Org version: 1.19.6
maximum request size:  16777212 bytes
motion buffer size:  256
bitmap unit, bit order, padding:    32, LSBFirst, 32
image byte order:    LSBFirst
number of supported pixmap formats:    6
...

Can anybody explain why the latter way works but the former does not?