looking at the amount of post that you have made means that you have played the game for some time!

and still you dont know that although it shows 5+5 gems
you get 5 gems for setting sail, and another 5 gems when you have made a completed sail!

therefore 5+5 = 10 in total

if you have made the completed sail and you only got your 5 gems for setting sail, then re-fresh your game and you will get the other 5 gems for completed sail