Maybe I should visit a monastery

A letter sent to all liturgical ministers at my parish church included several notes on procedures and practices. The following admonition startled me:

Out of respect for God and the people assembled to worship, it is very important that all liturgical ministers keep always a proper and modest attire when serving. No tennis shoes, jeans, shorts... Ladies, please, no low cleavage. Blouses, shirts and skirts should be modest at all times, no matter what is the occasion or in what ministry you serve. All of us, women and men, must strive to bring people’s attention to God, not to ourselves.

So… "high" cleavage is okay?

…and should I be proud or concerned that, at 37 years of age, I'm not sure I understand what is meant by "low" cleavage?