If you are "under the retirement age for this plan", it means you are receiving plan benefits even though you do not meet the minimum age at which you could normally  retire under this plan.

This occurs when you are unable to work to normal retirement age (disability), but otherwise qualify to receive a retirement benefit. Until you reach the minimum age at which you could retire under your plan, your payments will be reported as "Wages" on your tax return.

So, 'yes' is to agree that I'm receiving benefits prior to reaching minimum age, thus, in my case, since I have survivor's benefits, 'no' means that I am over that minimum age, even though my beneficiary might not be?