Believe the CRM. It is downstream of a person doing a job, and the dashboard is upstream of an assumption.
The gap is almost always one of four things, and all four are findable in an afternoon.
Work through it in this order
Is the form event firing on submit rather than on success?
The commonest single error. Every abandoned and failed submission counts as a lead, and the inflation can be double.
Owned by Tracking and attribution
Are duplicate calls counted separately?
One person ringing three times is three calls and one lead. Whether the platform de-duplicates matters more than any other setting.
Owned by Tracking and attribution
Is the lead source reaching the CRM record at all?
Usually it is not, and the field sits empty. Without it, nothing can be reconciled at the job level.
Owned by Tracking and attribution
Is profile traffic being counted as site traffic?
An untagged Google Business Profile link lands in organic and the site work gets credited with it.
Owned by Tracking and attribution
Reconcile the counts before you judge any channel. A reported cost per lead built on a number twice the real one has been wrong in the same direction for as long as it has existed.