Report limited to 4000 records?

Report limited to 4000 records?

I have a form with over 8000 records. Every record has a field "Type" which is required (always filled). I created a report to show the counts per "Type". These counts add up to 4000 (I expected the total to be the same as the number of records in the form, over 8000).
Is there a limitation in reports that a report doesn't process more than 4000 records?

please advise
Henk