First you need to create a new field like described in the chapter Create and configure fields. Then you go on the field settings tab. You should now see the following:

 

 

Here you can enter a default value for the field value as well as a maximum field length.

 

Mask...

 

You can read more about how to create links to your table in the chapter Linking fields.

 

Furthermore you have the possibility to use automatic numbering for new data records. Tick Use automatic numbering - only for new records to activate this setting. In the prefix field you enter the characters the numbering will always start with. In the first suffix field you can only enter a number, in the second suffix field there is also the possibility to enter characters. These suffixes are always at the end of the numbering.

 

In the end you go on Save.

 

For some field types you have another tab called Field triggers where you can apply more settings.