Here is the note Mike and I received from Kristjan:
The final number of e-votes is 104,415. I also received an approximate size of the electorate from the Electoral Commission. It slightly varies on a daily basis and it is larger than the electorate for national and EU elections – namely, in local elections also those can vote who live in Estonia with the permanent residential permit (i.e., russian minority mostly). So, the current size of the electorate is 1,094,326 voters, which means that about 9.5% of the electorate voted online.
BTW, he also noted that, given that local elections have about a 50% turnout, this means about 20% of voters will vote online.