Suffix For Room Numbers
This is a counter that can be used after numbers to let you know what number room it is. It's a room number that you use in apartments and hotels to know exactly which room you're looking for.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
room number one
This is Room 302.
Can you come to Room 103 in Hotel Tokyo right now?
The head office is located in Room 507 in that building.