The amount of calcium typically seen in an API SM engine is close to 2ooo parts per million. This comparatively high number is typically driven by the detergent additive. To contrast this level of calcium with others engine oil specifications, consider an API SA engine oil would have no calcium (therefore no detergent additive.)
It is also important to consider that whereas a high level of calcium may be desirable due to the lubricant's detergency, too much detergent can result in an oil with a high ash content. And when it does, in addition to acting as a detergent, the detergent itself can also contribute to lubricant contamination.