Dwarven Fighter with 19 CON gets 15HP
Dwarven Fighter with 20 CON gets 16HP
To arrive at it you have to use an extremely complicated and difficult forumula
. You see a fighter gets 10HP per level. 19 CON gets you an additional 5. 20 CON gets you an additional 6. To see how much additional HP you get from CON check table at the back in your manual. Race has no effect.
Keep in mind this only works up to level 9. After that fighters get 3 HP per level no matter what is their CON.