。
Make sure you're here by the appointed time.
Literal
Promise [gen-の] time [by-までに] without-fail here [to-へ] come [purpose-ように].
~ように at the end of a sentence, detached from any main verb, functions as a directive — 'make sure that X,' 'see to it that X.' It's an indirect imperative common in written notices and formal instructions. までに ('by (a deadline)') contrasts with まで ('until'): までに is a deadline, まで is a continuous endpoint.