Not 精通, but know a little.

Defined Benefit Plan is  calculated based on retirement policy of your company. In general, average annual compensation of last 5 years prior to termination of employment, years of employment, etc. are factors on calculating the benefit.  The formula is not universal but company specific. The key to this plan is that plan sponsor (your company) takes market risk.   It is as opposed to defined contribution  benefit plan that plan members take all market risk (such as 401k).

Hope this help.