You just have to start making all or most of your moves faster. I believe that statistic is now calculated over the last 90 days and it is just the average of the times between when your opponents move and when you make your move.
With a time/move as low as yours, you probably need to get 80-90% of your moves completed within an hour or two of your opponent making their move in order for you to actually start seeing that drop.
Or you could start moving more slowly on all your moves and the value should increase. However, the more completed games you have in that 90 day window, the harder it is to move the value.
How do I get my time per move down? I make my moves on a timely basis and the tpm never changes. Is there anyplace where I can see what data is used to calculate it? If I saw the data, then I would have a better understandin of why the rate never changes.