Delta Generic Extractors

I have created a Delta enabled generic extractor which is based on a view.

1. The view is a join between a Z table and EQUI.

2. I have taken all the fields from the Z table and EQUI-AEDAT (Date of Last Change).

3. I have delta enabled the extractor using the Calendar day option choosing AEDAT

4. I have not set any safety interval limits

5. We have carried out an Init which was successful

6. We carried out Delta loads where no changes were made and got 0 records

7. We made some changes today and expected the Delta load to reflect these changes but we still got 0 records

Is a safety interval set automatically? If so how can I check and is it possible to change? Thanks