Paul – the SMAT counts are a bit confusing, but not necessarily misleading. The searches you specify are carried out against the entire file being viewed, not just those you have “selected”. So, when you select 78 out of 1000 messages, and add them to your view, and then want to further filter them, SMAT carries out your instructions against the 1000 messages, not just against your selected 78 messages.
Takes a little getting used to…