Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 160; Flight Crew Type 3000
Situational Awareness; Human-Machine Interface; Confusion; Communication Breakdown
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance; Flight Crew Requested ATC Assistance / Clarification
Procedure; Chart Or Publication; Human Factors; Software and Automation
We were sent a CPDLC (Controller Pilot Datalink Communications) that cleared us to CHS. Instead of using the load function we selected direct to CHS. ATC queried if we were going direct to CHS. We responded affirmative. He then informed us the clearance in the CPDLC was to CHS via FKN. We both missed the FKN part of the route clearance. Asked if he would like us to go direct to FKN then CHS he responded no. We looked at the CPDLC and both had misread the clearance. The verbiage on the CPDLC was in my opinion a little confusing and the FKN showed up on the bottom left of the page after 'CLEARED TO CHS.' FKN was not on our file route. We didn't hear any vectoring of other aircraft do to out flight path.
Upon reaching cruise altitude; we received a CPDL (Controller Pilot Datalink Communications) clearance that read in top line; 'cleared to CHS via route clearance'. Next line free text; 'Rest of route unchanged'. Next line free text 'Cleared to CHS via FKN CHS.'  As Pilot Monitoring; I read first and second lines and due to expectation bias; immediately told my F/O; 'Cleared to CHS'  I then went to next page and hit Send.  My First Officer went to LEGS page and pulled CHS to top and executed.  Both of us missed FKN inserted into new route clearance.  We were later questioned by ATC.  After rereading CPDL clearance; our error was clear.
A Flight Crew reported a route deviation due to confusion between the clearance issued by ATC versus what had been issued via CPDLC.