When I bring up the map I see a number on top of each region. Is it indicating number of diamonds or suitacases hidden in that region? Some suitcases contain several diamonds.
The number indicates how many diamond cases are in the region, not the total number of diamonds.
Reference: http://farcry2.wikia.com/wiki/The_Far_Cry_2_FAQ under "Finding 'loot' via GPS?"...
"Note that in the top left of Zone maps there is a blue number on a black square. It tells you the total number of Diamond Cases in this Zone."