The sign above the terminal has numbers, I assume, to help the pilot park. What do they all mean?
That's a countdown to the Target Off-Block Time (TOBT) showing 67 minutes to go. The minus is like the T minus 5 for a rocket launch.
[TOBT is the] time that an Aircraft Operator (AO) or Ground Handler (GH) estimates that an aircraft will be ready, all doors closed, boarding bridge removed, push back vehicle available and ready to start up / push back immediately upon reception of clearance from the Tower. (...)
TOBTs will be displayed on the Stand Entry Guidance System (SEGS) for every flight at 'Actual in Block Time' (AIBT) or 75 minutes before a departure. The countdown clock is in line with the latest TOBT update. Please see Fig.2 [emphasis and link added]
The display design will vary from airport to airport.
Since in your photograph there's no jet bridge (no actual docking), the display is mounted separately and is not used for parking guidance. Thanks to @fooot for identifying the airport, here's a press release on SEA's general implementation.
The guidance (and information) system at SEA (where jet bridges are used) uses "infrared laser and patented 3D scanning technique" to identify the plane type, distance, and orientation – unlike the older left/right parallax-based guidance.
This is at Sea-Tac Airport in Seattle. The -67 indicates that the flight is supposed to depart in 67 minutes, and gives flight info like flight number, destination, and updated departure time. This is used more for the ground staff. Everything works on a timeline. At Horizon air, where this is pictured, the process usually begins at 40 minutes prior to departure (minimum turnaround time for us). Boarding begins at -30, and ends at -12. If all goes well, the brakes are released by the time the counter reaches 0, which determines the on-time status of the flight (at least for the company, now it's up to ATC to get the flight out). Only the C gates at SEA have the display.