'Multi select' can be used to make a selection of tables the same size as the first table you select.
Consider this example. We are going to make tables 8, 9, and 10 the same size as table 7:
1. Click table 7.
2. Click 'Multi select'.
3. Click tables 8, 9 and 10 in succession. You will notice that new buttons (shown below) become available when you click the first of the additional tables.
4. Click 'Same Size'. Tables 8, 9 and 10 are now the same size as table 7.
5. Click 'Save' to save your changes.