You may use the Use ID Generator Field form element to generate to create a running number in your form design.
Figure 1: ID Generator Field propertiesProperties
You can specify the name of an existing environment variable to be used as the number to be incremented everytime a new form is created. If the environment variable that you specify does not exist, Joget will automatically create a new one for youJoget would create a new Environment Variable if it doesn't exists. The value of the running value will be stored in the App's environment variable. You may check on the current running value in the Appof the counter you specified in your app's properties tab.
Figure 2: Environment variablesVariables
Every time the form is submitted, the element will generate the next running number from the environment variable you specified and will place it into the field's value. You may also write the value into a workflow variable.