Creates too much precision for unrelated commodity

```
2020-10-23 * "Test"
    Assets:Property                   0.11111 FOO {300.00 EUR}
    Equity:Opening-Balance
```

leads to

```
2020-10-23 * Test
  Assets:Property                                  0.11111 FOO {300.00 EUR}
  Equity:Opening-Balance                                    -33.3330000 EUR
```

The precision for EUR is wrong.
