What does “and counting” in “Bits of plastic in oceans: 5.25 trillion and counting” mean?

Today’s (December 11) online New York Times carries an article dealing with the quantum increase of plastic material in the ocean under the headline, “Bits of plastic in oceans: 5.25 trillion and counting,” followed with the lead copy;

“New computer modeling suggests that plastic particles weighing almost 269,000 tons are floating in the world’s oceans.”

Though it may sound a very naïve question, how can I take the word, “and counting” here?

Does it mean 5.25 trillion bits of plastic is “being counted,” “still on increase,” “a serious matter,” or else?

English dictionaries at hand include too many definitions and usages of “count,” and I can’t judge which one of them is applicable to the above headline.

The phrase “and counting” was popularized by the old pre-launch countdowns of the U.S. space program; it meant that the number of minutes or seconds till launch was actively in process of decreasing. (If the countdown were stopped, the number of minutes or seconds remaining in the countdown would be followed by “and holding.”) In the case of oceanic trash, the number of items is said by this phrase to be in process of increasing.

In this case ...and counting means that the number is continually increasing with time.