Pressure Cooker Whistles in Indian Recipes

Many Indian recipes indicate cooking time in a pressure cooker as "two whistles" or "three whistles". How does that translate into minutes, or is it variable depending upon what's in the cooker? I have a recipe for goat curry that calls for 4 whistles. Does anyone have any idea how long that would be? What we have is cubed, bone in, tough, old Halal goat, but it will have been marinated overnight. When we tried to cook it on the stovetop once, it took over two hours. And, is it crazy to try to cook 5 lbs of this goat meat in a Tramontina 6.3 qt pressure cooker? Any suggestions would be most appreciated. Thank you.