FIRSTDATE nor working

Guys,

I am working with a date table, and looking for the first and last date of a table.

As you can see in the attached image, I have an interval form 01/01/2021 to 05/01/2021; the issue is that with the FIRSTDATE command I was expecting to have one value, the first date on the interval. The result is the exact same table from the slicer in the top right. I tried with LASTDATE as well with the same results. Is this a bug? According to the DAX command description, I should have a table with a single column and a single row.

Thanks, regards,

Abelardo