There's a line in the document that says:
"When it previously rendered, the `Calculator` has specified that"
The sentence is using a present tense verb ("has"), but the statement is in the past tense.
I think "When it previously rendered, the `Calculator` had specified that" would be correct.
* Added ellipsis to indicate incomplete code snippet
Ellipsis indicate that the code snippet shown is part of a larger code sample.
* Add missing indentation