Delayed Pension Application and Tax penalties

My Folks have a strange situation.

My dad worked many years as a union carpenter before he switched occupations 20 years ago.. About 10 years ago he became eligible for a small defined benefit pension but never applied because he lost touch with his union. He finally applied a month ago and will soon receive a monthly check of around 500. That's fine and dandy.

However according to the bylaws of the pension he is entitled to money he was supposed to have started collecting 10 years ago. that’s roughly about 60 thousand. If he has to pay income taxes on it, no problemo and that's expected.

Here is the problem:

5 years ago he turned 70 1/2. Since that time it was mandatorilly required by tax law he collect his monthly pension benefit or suffer a 50 percent tax penalty.

So the question is this. does he have to pay the 50 percent tax penalty on the whole 60 thousand since he will get it in one lump sum now, or just on the 30 thousand since 5 years ago?

The union rep gave him the option of having an increased benefit without a tax penalty but it he would have to live another 100 years or so to collect it all.

He is confused and so am I.