You Can Tell a Lot from a Courtroom Number
The Philadelphia criminal justice system has two components: the Municipal Court and the Court of Common Pleas. The simplified version of this structure is that the Municipal Court is the lower of the two courts, and handles misdemeanor cases, while the Court of Common Pleas is the higher court, and handles the more serious felony matters.
To make things a little more complicated, the Municipal Court conducts the preliminary hearings for all felonies, before the actual trials in those matters are held at a later date in the Court of Common Pleas. As an organizational matter, the Municipal Court conducts these preliminary hearings in courtrooms both in the Criminal Justice Center in Center City (the "CJC" in court lingo) and at various police district headquarters throughout Philadelphia. Conversely, for the misdemeanor matters the Municipal Court controls, it conducts a brief status conference in CJC Courtroom 404 before setting a date for the trial.
Thus, by looking at the courtroom number on the piece of paper you got in the mail ordering you to appear in court, you can tell how serious the charges against you are:
If you have been ordered to appear in CJC 404, you know you are not being charged with a felony.
Conversely, if you are being ordered to appear for a hearing at the 8th Police District Headquarters in the Northeast (or any other courtroom other than CJC 404) you know that you are facing at least one felony charge.