You may want to have more pension in your early years of retirement and subsequently a lower pension; or vice versa.
You may opt to have a higher pension for the first five (5) or ten (10) years of your retirement, and subsequently a lower pension. This could be useful if you stop working early and are not yet receiving a state pension (AOW); or if you have children who are still studying. Your low pension would be 75% or 90% of your high pension.
You may opt to have a lower pension in the first five (5) years and subsequently a higher pension. This could be useful if you have a higher income in the early years of your retirement, due to an annuity for example; or because your partner is still working. Your low pension would be 75% or 90% of your high pension.