Hi Vicky. This sounds very much like my recent protocol.
I had 33 radiation treatments over 47 days, and 7 lower dosage Cisplatin chemo infusions weekly.
I could have opted for 3 larger doses, but I felt that the lower doses would be easier to tolerate, even though more frequent.
Generally, I think the effective smaller doses are 40mg each, and the large ones are effective 100mg each.
Now, this is important, the reason that I say, "effective dose", is because the actual amount of drug is based on your height and weight.
So my infusion bag showed 78mg, and I was getting nervous that I was getting the wrong dose for 7 weeks. But the Oncologist explained the adjustment to me, and I also found a dose calculator online, that eased my anxiety.
And the reason that I had 7 infusions, not 6, was because I started mid week, and there was also a holiday, so my last treatment was just shy of 7 full weeks.
Best wishes that everything goes well with your Dad. It's very good that you are making sure you understand everything. I suggest running by the Oncologist, what I wrote about the 40mg weekly dosage, and the height and weight adjustment.