Summoning mobs with custom health is +1

When summoning a mob using generic.maxHealth,Base:X, the health is X+1.

The exact command I was using is

/summon Wolf 2 164 -5 {Tags:["TeamMob"],Attributes:[{Name:generic.maxHealth,Base:1}],HealF:1,PersistenceRequired:1,NoAI:1,Silent:1,ActiveEffects:[{Id:14,Amplifier:1,Duration:1,ShowParticle s:0b}]}

but it can be replicated with even

/summon Wolf ~ ~ ~ {Attributes:[{Name:generic.maxHealth,Base:1}]}