in civiBooking, additional text is showing under Resource Configurations while trying to add a booking.
It looks like that text is likely from the "Resource configuration size unit" option list.
From the Resource Configuration Set page (civicrm/admin/resource/config_set?reset=1), you can edit the individual options for the configuration set in question. You can select a different "Unit" on the options, which shows up at the end of the selection as you noticed.
If there is no appropriate option listed, you can also edit the option list that is used here. Go to Administer > System Settings > Option Groups and look for the Resource configuration size unit group.
It looks like you've already set these values correctly. Did you change the values at some point? If you create a new "size unit" and select that, does it affect the display?