How to smoothen the counter display

Hi, I have a input from a source which gives me a count every 1 second (usually 3 to 5, maximum 6). I want to totalise this and display as a cumulative counter for one minute and reset. currently the Minute counter displays like, 5,10,15,19 etc depending upon the first input.
what would be the way to display the Minute counter as 1,2,3,4,5 so that the counting is continuous and smooth ? current display and expected display shown below.
Current Display

Expected (simulation here)

If i understand correctly

I would use the browser and some javascript to do this. Maybe feed in the new value to the browser and have the browser JS update the display value till it reaches the new value.