National Pension Act Article 19

Payments of the insurance shall be calculated based on the monthly insured amount for the specific month when contingencies happen.The calculation basis for pension payment shall be adjusted when adjustments are made to the monthly insured amount.
中文原文 國民年金法第19條
本保險之保險給付,按保險事故發生當月之月投保金額計算。
月投保金額調整時,年金給付金額之計算基礎隨同調整。

English translation for reference only; the Chinese text prevails. Not legal advice.