Different alignments of columns in v-data-table

[xtrailrunner]

Hello,
I've just started to use Dashboard 2.0 with th v-data-table component.
I have a simple table with two columns. First column displays labels and should be left-aligned. The second column displays numerical values and should be right-aligned.
This construct in ui-template has no effect:

        headers: [
          { text: 'Speicher', value: 'speicher', align: 'left' },
          { text: 'Wert', value: 'wert', align: 'right' },
        ]

The following styling aligns both columns

.v-data-table__tr {
   text-align: right;
 }

Can you pls. recommend a way to align both columns in a different way.

regards
Juergen