The clerk sent a notice out on May 4, 2012 in the case (on "complaint number 1", to distinguish it from any additional complaints filed by any other party in the case--usually there is only one complaint). The notice was to advise the parties in the case about the outcome of service of the summons and complaint upon the defendant named in the suit (i.e., whether the defendant was served or not served). ATP means "attorney for plaintiff." If the defendant was not served, then the notice only goes to the attorney for the plaintiff, since that is the only party officially appearing in the case so far. When the defendant is served (is that you?) you will then receive copies of any court notices in the case.
Without reviewing the entire document, it may be difficult for any attorney to answser your question. Chances are from what you have state, you have been sued and a complaint has been filed with the court. AYou will be served with the complaint by some means - either sheriff, process server or by certified mail. I am not admitted in Maryland so I don't know the specifics. The time to answer runs from the date you actually receive the complaint, not the date on which it was filed. If you are concerned, then you may want to go to the court, make a copy of the summons and complaint and take it to a Maryland lawyer for review.
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