A classic case is not correct

[jeffwadsworth]

https://gatherer.wizards.com/pages/card/details.aspx?name=humility
If you play Opalescence, Humility, and another Opalescence, your project will incorrectly have them as included in the picture. They should be 4/4, 4/4, and 1/1 for the last Opalescence.

[Soothsilver]

This is ok. In this tool, "Opalescence" is coded as "Other enchantments have base power/toughness 5/5" instead of "Other enchantments have base power/toughness each equal to their mana cost". For the purposes of layers, the actual power/toughness doesn't matter, and this tool doesn't keep information about mana cost of permanents.