The rules that use the vocabulary item "twenty" are:

<hour-not_initial_zero>

twenty

twenty one

twenty two

twenty three

<scale_number>

twenty five hundred

twenty thousand

twenty five thousand

<hour>

twenty

twenty one

twenty two

twenty three

<tens>

twenty

<up_to_thirty-pl>

twenty

twenty <digit-not_zero>

<tenminutes>

twenty