If Mary's heart scan score increases from 2 to 4 in one year, it represents a 100% increase in score.
If Jane's heart scan score increases from 1002 to 1004 over the same period, it represents <1% increase, even though the true growth is the same: 2 points.
This quirk of arithmetic needs to be factored in whenever you and your doctor try to puzzle out the meaning of an increasing CT heart scan score. Lower numbers, particularly those <100, can grow at seemingly much faster rates if viewed by percent per year increase. If no effort is taken to stop the growth in your coronary plaque, then scores of 10, 20, 30, or the like can easily grow 50-100% per year.
In contrast, scores of 1000, 1500, and 2000 tend to grow at "slower" rates of 20% or so per year without corrective efforts, even though the absolute growth may be substantial. (Obviously, this bit of confusion can be best eliminated by reducing your heart scan score, but it doesn't always work out that way.)
If we were all adept at advanced math, we should probably rely on logarithmic measures of plaque increase, rather than percent increase. Or, you can just keep in mind that the rate of plaque growth must always be viewed in the context of the absolute score.