Title is misleading, FTA:

Confirmation that I am 63% British and Irish, 17% Danish and otherwise “broadly north-western European”. I felt a resounding ambivalence about the results, including some disappointment that I had not discovered a newfound heritage – a piece of information that would give my identity new dimension.

But also:

My father’s side of the family is meticulous about tracking our ancestry, with records that hold the name of the exact small village in Ireland our ancestors hail from.

Those results often can't narrow down to exact countries so it says he's 63% British and Irish. Seeing as his fathers family has records of being from a small Irish town it's likely he's more Irish that British, not that it means anything if you're actually American anyway.