Information provided by Hari Dharam Kaur Khalsa

1. In the Siri Guru Granth Sahib, the word “ghar”  (Gru)   is often used.  Literally, this word means “home”, but in this case it means the tune, musical notation, or beat that a particular shabad is to be sung with.  These musical notations denote the pitch of the notes according to the musical notation of the specific number accompanying the ghar.  The number of this type of musical notations in the Siri Guru Granth Sahib goes up to 17. (Per “Sri Guru Granth Sahib Darshan” by Bibiji )
2. In the Guru Granth Sahib, the caption of each set of compositions under any raga contains the name of the author (Mahla) and the Ghar. The word ‘Ghar’ has been interpreted by scholars in different ways. According to Bhai Kahn Singh, it has two meanings. First, it indicates the tala (rhythm-pattern) and secondly the sargamparastar, the singing of a poem according to a certain style or tradition. (Per Mahankosh, p. 441)

See a list of the Gurmukhi Ordinal Numbers Here