en frá lánganesi á norðanverðu íslandi er IIII dægra haf til svalbarð a norð í hafsbotn
As of today, it is unclear what this "svalbarð" really is: unlikely to be Jan Mayen, since far too small and insignificant to be mentioned, certainly not the already known Greenland, possibly today's Svalbard (the navigation distance of 4 days from the North coast of Iceland is correct) - if not just the edge of the ice shelf, which would match the name incredibly well… The discovery of Svalbard this early is just a possibility, not a factum.
The presence of the Pomors on Svalbard during the 16th century is also not proven, and the first certain discovery of the archipelago is Willem Barentsz's third trip to the North, 1596. He named the place "Spitsbergen", the "jagged country" because of the jagged mountains on the West coast, but it was prosaically renamed to "Het nieuwe land", "the new country", on maps published soon thereafter.
I have discovered the jagged cold coast for myself this year.