Ubuntu – Crontab error “No crontab for root”

when I write crontab -e command in terminal,

I get this error message:

no crontab for root - using an empty one 888

I don't know what '888' is meaning?

Config file of crontab /etc/crontab:

# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file
# and files in /etc/cron.d. These files also have username fields,
# that none of the other crontabs do.

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# m h dom mon dow user  command
58 * * * * root cd / && run-parts --report /etc/cron.hourly
52 0 * * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
46 0 * * 7 root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
9 5 28 * * root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )
#

Please help me.

Thanks.