Let's consider a scenario in which you call the API to get new jobs for the past two days, that means that every time there will be some overlap. If the API returns the same job a second time, we will display the job to you but we will not deduct the job from your job credits.
However, we provide a timestamp-like parameter called "cursor" using which you can receive only new jobs since the last query you made. API response also returns the next_query. So instead of querying for last 2 days, you can query since last cursor value. More details on the API can be found here.