Hi,

In order to achieve that, you should select the following Field properties:

1. Default (F11 key): Highest +1

2. Unique: So it creates automatically a DB index on this field, to not allow repetitions

Example:

Remark: List of possible defaults start at position 0, so it will appear the alias of the type Numeric and position (N) 3 when you select the default. For instance, if you select the first option it would be N 0.

If you want this behavior, but inside a series (let's say you want to have several lists running and their numbers can be repeated, if they belong to different groups), you can fill the field property "Prefix non-duplication" with the table column that represents that group.

Hope it helps