Dan and I have had a long discussion about this in another thread (and we agreed to disagree!). It is to do with what moodle counts as an attempt.
Moodle counts each opening of the scorm object as an attempt. Where as captivate (and other authoring tools I believe) count each run through of of the module as an attempt.
For a fuller (and duller) description of this with examples please see https://moodle.org/mod/forum/discuss.php?d=206692&parent=1294716