Answer based on context:

The Dutch garrison of Recife was increased in March 1640 by 2,500 soldiers carried aboard 28 ships under Amidrals Cornelis Jol and Jan Lichthart, who was in charge of naval operations to disrupt the Portuguese sugar trade. In December Portugal revolted against the Spanish Habsburg rule, proclaiming the seventh Duke of Bragança as King João IV in place of Philip IV of Spain. Although the Dutch welcomed the news of the revolt, expecting the Portuguese to become their allies, this did not happen, as the Dutch had no wish to restore the occupied territories to Portugal. Recife served as base for an expedition under Jol and Lichthart, in 1641, to seize Portugal's slaving depots in Angola before any treaty could be concluded in Europe, and despite a ten-year truce between both countries that was signed on 12 June, the hostilities continued, resulting in the expulsion of the Dutch from Brazil in 1654.

How many years was the truce supposed to last?
10