Legislative size (voting members)

Representation of the People Act, 1964, http://www.gecom.org.gy/pdf_laws/REPRESENTATION%20OF%20THE%20PEOPLE%20ACT.pdf

Inter-Parliamentary Union ParlineDatabase:Guyana, http://www.ipu.org/parline-e/reports/2135_A.htm

Representation of the People Act:
Section 11(1): The National Assembly shall contain sixty-five elected members, and their election shall be on a party lists basis to which the system of proportional representation shall be applied; in this section and in section 11C the system of proportional representation referred to is known as the largest remainder system using the “Hare quota”.

Inter-Parliamentary Union Parline Database:Guyana:
A maximum of four non-elected ministers and two non-elected Parliamentary Secretaries may sit in the National Assembly. If the Speaker is not an elected member, he or she becomes a member of the National Assembly by virtue of holding the office of Speaker. The National Assembly may thus have up to 72 members. 

NOTE: There are currently 67 members of parliament, 65 of which directly elected (http://www.ipu.org/parline-e/reports/2135_A.htm).