The thumb is much smaller than it should be, and the forefinger is too large. Also if you make that figure with your hand, you will notice the thumb curves with the palm, there is a dip just below the thumb which should curve with it. And the connection of the fingers, were the fingers all come together you wouldnt see in the reference, thats not were you would see it, the skin from the thumb would curve like a golden ratio. Other than the porportion and placement issues you did well making it realistic. Also you have short time periods for a reason, try going with 1 to 2 minutes and not at all focusing on the realism just accuracy.
whitebrowpygmy