And the Estimate is not a hard number. In the desert, the battery operates in a warm condition. In the winter, the battery may operate in the bottom of its heated/cooled range. The Estimate will be figured at battery temp, that could vary fill by fill. Losing 1/223 miles is in the noise level of estimates. I would bet that setting your charge to 90% has some wiggle room in it - Could it be 89.5% one time and 90.5% the next?
I remember one fellow saying "measure with a micrometer, mark it with a piece of chalk, cut it with an ax".