A more thorough explanation:

A sealed verdict is a written decision made by a jury before it is read out loud in court. The verdict is kept secret until the court reconvenes.

After deliberating for several hours, the jury reached a sealed verdict. The judge dismissed the jury and scheduled a time to reconvene and read the verdict.

Another example could be:

The jury was unable to reach a verdict before the court's closing time. They were instructed to produce a sealed verdict and return the next day to hear the verdict read aloud.

These examples illustrate how a sealed verdict is a written decision made by a jury that is kept secret until the court reconvenes. It allows the jury to disjoin while the court is out of session until the next point at which it reconvenes.