This article was previously published under Q298915
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When you try to alter the percentage of the amount of disk space System Restore uses, some percentage numbers may be repeated or missing when you move the slider from Max to Min.
This behavior occurs because the user interface allows you to specify the disk percentage where it lines up on one of the "tick marks" on the size slider. Because numbers are rounded off, the tick marks might not line up close enough to a specific percentage number (depending on the size of your drive). There are 11 tick marks on the slider, but there are 12 whole number percentages that can be displayed (1 to 12), so one of them can be missing. Because of this, and depending on the size of the drive, some percentage numbers might be missing or might be repeated. The user interface attempts to divide the partition space into 11 portions that line up with the tick marks on the slider. It also rounds off numbers to only display whole number percentages. The first tick mark is the minimum data store size, normally 200 megabytes (MB) for the system drive, and 50 MB for non-system drives. The last tick is the maximum data store size, normally 400 MB or 12 percent of the drive, whichever is greater.The "missing" percentage problem only occurs if the minimum data store size is less than 2 percent of the drive, because 2,..., 12 is a list of 11 whole numbers. For system drives, this is 10 gigabytes (GB) (200 MB divided by .02), and for non-system drives, this is 2.5 GB (50 MB divided by .02). If the minimum data store size is greater than 2 percent of the drive, then there are enough sequential whole numbers (and perhaps some that are used more than once) to label the tick marks. If the minimum size is less than 2 percent, the user interface may be missing some whole numbers.