These decisions hold until ratified or rejected by the court as a whole (which they all eventually will, but it's not fast) or successfully appealed. Appeals can be made only to another Justice or to the court as a whole - no expedited process, because there's no higher authority.
Besides, who'd make the appeal? X has no representation in Brazil (that's why it's been suspended), and there seems to be consensus on that specific point, of legal representation being a requirement by law, so the general attorney or other officials will not question the main decision.
The side decisions are a different matter, that about VPN apps and app stores had been withdrawn. The fine for accessing X is more controversial: hardly enforceable (for just browsing, at least), ongoing hot debate in the country about it being within the Justice's power.
In fact, the Court will probably expedite a whole court judgement on that, and apparently there's no consensus across the Justices on that.