That's quite impressive. I looked up the German Corona app on the play store and they have 5 Million total installs on a population of 80 million. The Apple store doesn't say.
I'm guessing we don't reach 20% though that Finland did in a day. While 42% of Germans said they would install the app [1]. There's a total of 17.5 million downloads (not installs) that puts an upper bound on current users [2].
I just wish there was more cooperation. In the EU at least there are so many apps and everybody is on vacation right now, limiting the usefulness of these apps.
[1] https://de.statista.com/infografik/22008/befragte-zur-nutzun...
[2] https://de.statista.com/statistik/daten/studie/1125951/umfra...