They list roles such as "Junior iOS Engineer" and "Head of Computer Vision": I imagine the low end applies to the former, and the high end to the latter (note that the market rates for Portugal also align with the lower bound).
Some of their job postings have tighter ranges (I only looked at two: one had no range, another had a tighter range), but the high end simply indicates that they are willing to pay for a great remote candidate regardless of the Portuguese market rates.
Ultimately, I do agree that a join of all the salary ranges for different positions is useless (you could include a janitor and CEO to make that $15k-$400k to make it even less useful).
Surely this is a typo, or else why post a range this vague?