Well - this post says that the Imataca is 3,800,000 hectares and according to presidential decree 13% of that is available for mining:

Imataca Forest Reserve

In addition to the general risks associated with environmental regulation and liability (see "Risk Factors -General Risk Factors - Environmental Regulation and Liability"), the Las Cristinas deposits are located within the Imataca Forest Reserve (the "Forest Reserve"). On September 22, 2004, Presidential Decree 3110, which establishes an ordinance plan and regulations for the use of the Forest Reserve, permits various activities (including mining) in up to 13% of the Forest Reserve and establishes the legal framework for such activities, was issued. Presidential Decree 3110 was issued in response to previous Presidential Decree 1850, the latter of which was issued in May 1997. Decree 1850 reserved an even larger part of the Forest Reserve for various activities and became subject to a legal challenge before the Venezuelan Supreme Court. The Venezuelan Supreme Court issued a prohibition order on November 11, 1997 prohibiting the relevant government authorities from granting concessions, authorization and any other acts relating to various mining activities in the Forest Reserve under Decree 1850 until the Venezuelan courts ruled on the merits of the nullity action. It is possible that Presidential Decree 3110 could be similarly challenged and that such challenge, if ultimately successful, could prevent the Corporation from exploiting or fully exploiting the Las Cristinas deposits.

Venezuelan Decree No. 1257 establishes the environmental assessment requirements for mining projects. The Corporation was advised that the Las Cristinas project is not a new project and, accordingly, Article 40 of Decree 1257 does not apply since no significant increase in environmental impact is predicted. (from KRY disclosures)

According to that math, only 494,000 hectares would be available for activities including mining. According to the article posted by CJR, Minamb is allowing 8 times as much as allowed by decree.