Putrid Goblin does not have a -1/-1 counter on it.
You have had at least one Zombie enter the battlefield under your control this turn.
Steps
Activate Blasting Station by tapping it and sacrificing Putrid Goblin.
When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
When Putrid Goblin enters the battlefield, Geralf's second ability and Blasting Station trigger.
Resolve the Geralf trigger, putting a number of +1/+1 counters on Putrid Goblin equal to the number of other Zombies that entered the battlefield under your cotnrol this turn.
Resolve the Blasting Station trigger from step 3, untapping it.
Resolve the Blasting Station ability from step 1, dealing 1 damage to any target.