What does "O.C." and "2/5 Portland" mean next to a Loyalist's name?

In the "Loyalists of Ontario" in the Ancestry Card Catalog, under the surname DAY, it says:
DAY, Barnabas of Kingston.
Barnabas of Kingston, O.C. 17 Nov 1797
Lewis of Kingston, m. Mary Hill. O.C. 17 Nov 1797.
David. Land Board Certificate, 2/5 Portland.

What does "O.C." mean and what does "2/5 Portland" mean?

Thank you in advance.