How to recreate
1. create any scoreboard objective and set any entity to have a value of 1500 in that scoreboard
2. shoot/summon an arrow
3. do the command, "/execute as @e[type=arrow,limit=1] store result entity @s damage double 0.001 run scoreboard players get @p <scoreboard objective name>
4. get the damage value of the arrow (/data get entity @e[type=arrow,limit=1] damage
5. notice how it is 1.0d, instead of being 1.5d
Comments 4
That's not the only mistake
scoreboard players get entity @p <scoreboard objective name>
"entity" is not a valid parameter here.
Please copy-paste the command you used, rather than retyping it.
Bytes don't allow decimals; it's an 8-bit integer (-128 through 127). You want to use a double, instead.
Invalid due to user error.