even if the AOBT may be advanced in 15 minutes, take
off shall not be permitted before the EOBT. (The Taxi-time
can never be negative)
It's rather odd because the CFMU phrase "taxi-time" is used, and indeed it cannot be negative. But taxi-time is a planning parameter that affects the earliest possible CTOT if a slot is issued. It is not related to ATOT or AOBT as is implied in parenthesis.