SMACK - subscription depth

I try to find the way to insert the subscriptionDepth in the database.

I 've got a SubscribeForm with some value :

SubscribeForm subForm = new SubscribeForm(FormType.submit);

                                        subForm.setDeliverOn(true);

                                        subForm.setDigestFrequency(5000);

                                        subForm.setDigestOn(true);

                                        subForm.setIncludeBody(true);

but I can find something like setSubscriptionDepth..

Someone can help me??