The note [0] (in Danish) published by the danish health authority with the reasoning for this puts the number a bit higher at around 5 to 10 per 1,000,000 [1], another thing that the note points out is if they start the vaccine program up with the AZ vaccine again, it may delay it in the older population even more as they think many people would say no to it.

[0]: https://www.sst.dk/-/media/Udgivelser/2021/Corona/Vaccinatio...

[1]: 1/40000 chance of serious complication with a around 20-40% chance of death, source: [0].