B737 flight crew is informed of track deviation after misinterpretation of PDC.

Narrative

PDC: -TERPZ1 JERES J220 VALLO- -KBWI TERPZ1 JERES J220 ZZZ. Incident: Departure from BWI was uneventful. Flight Plan Route was to VALLO waypoint (first line of PDC) and then Flight Plan Route direct ZZZ (second line of PDC). When our flight reached VALLO waypoint and turned directly toward ZZZ; ZNY inquired on why we were deviating from J220 and requested we return to our Flight Plan Route of J220 to ZZZ. We were then asked to call ZNY. I talked to the Center Supervisor and he stated there had been several incidences regarding Flight Plan Routes and the PDCs. I explained our interpretation of the PDC and why we turned direct to ZZZ. Suggestions: The PDC that we were given leads you to VALLO and after VALLO direct to ZZZ. I believe that this could be eliminated if the PDC were as follows: -TERPZ1 JERES J220 VALLO J220-. With this corrected PDC there is no discrepancy on where your flight plan leads after VALLO and you are to resume J220. Example: Our following PDC out of ZZZ: -V115 JHW EWC- ZZZ JHW EWC J53 PSK CAE J51 SAV J103 OMN. There is no doubt on your flight plan with this PDC; it is very definite and explanatory. I believe the vagueness of the PDC led to this Flight Plan Route deviation.