This issue relates to the display of stats in tool/weapon descriptions. As far as i have tested, it does not have an impact on how much damage is actually dealt.

Wooden Sword
+3 Attack Damage
-2.4 Attack Speed

Player's Base Stats (Modified using /attribute for the purpose of showing the bug)
10 Attack Damage (Normally 1)
10 Attack Speed (Normally 4)

Combined Stats
13 Attack Damage
7.6 Attack Speed

As you can see from the attached image, Attack Speed is correctly displayed, whilst Attack Damage is not. Note that this bug is encountered in both creative and survival, as the increased damage from the Strength buff is not listed either.

Commands used
/attribute @s minecraft:generic.attack_damage base set 10
/attribute @s minecraft:generic.attack_speed base set 10