I have noticed that the multi-row card does not take into account the format string of a field, whereas other visuals such as table and matrix do. See screenshot below, on the left is the multi row card displaying these fields in the default number format, whereas on the right the same fields are in a table and the SSAS format string displays correctly (has been customised for Swedish krona currency).
Modifying the format string in SSAS updates the format in the table on the right but has no effect on the multi row card. There also doesn't seem to be a way to change the format in PowerBI, maybe because it's in live mode. I am connected to an SSAS database in live mode, using the latest PowerBI Desktop RS ver. 2.51.4885.2501