Good to see a MM being employed. Curious? Are you simply pulling splits out of your stack and applying the meter to the existing outside surface? If so it means next to nothing in most cases. Not to be argumentative (useless endeavor) here but each split that you test needs to be re-split and tested on the freshly exposed inner face for any semblance of accuracy. If not its a waste of effort with useless results. My experience. Good luck and let everyone know the testing method being shown.