Since it currently is a lighttower study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7456194/
If I calculate it correctly, the used dosis of 0.532 mg Vit D3 equals 532 mcg equals
21,280 IE .
Another study with a population of almost 9000 patients has been done in Israel meanwhile. Its conclusions point at the same direction as the Spanish study.