Make sure you are looking at the correct damage area for healing bombs.
The amount a healing bomb will heal is the 2nd number in the damage area and whatever forge effects have been added as the first number is what it would had done if it was a normal bomb to the blocks it hit.
In this case the bomb would normally heal for 2,000 but it also has +1,500 heal added from forging so 3,500 in total.
They do have an issue not hitting you at times even if you are standing on it so it’s not a desync issue like it can be when trying to heal others that move so they do have issues and I am not sure why you are getting different amounts like that.