No, I mean I am flying level, VS indicator shows level, and I happen to notice that my altitude is adjusting either up or down. When I press B my QNH has changed. The pressure has changed as I was flying along. Sometimes its a small amount, sometimes several hundred feet.
I’m not repeatedly pressing anything. I am noticing a relatively rapid change in indicated altitude even though I am in level flight, and its because the QNH has changed.
I just finished a flight from New York to Washington, and spotted this as I was descending for arrival.