I created a Warforged Cleric of the Forge Domain using the official D&D Beyond tool. It came out with 15 HP at level 1. Where did the extra 4 HP come from? I have a Constitution score of 17 (a +3 modifier), so it should be 8+3=11, right?
I also re-made the character using the Fight Club iOS app, and that app shows the character as having 11 HP.
What am I missing?