Medicare supplement /"medigap" coverage outside of US

Hi all...

I currently have a high-deductible Plan F medigap policy. As with all Plan F policies, travel outside the US is covered with an annual $250 deductible, and 80% of eligible expenses are paid up to a lifetime maximum of $50,000. Coverage is provided for the first 60 days of a trip outside the US.

I've been searching for more information on that last item.. the 60-day limitation of coverage. I haven't been able to find out much at all so far. I'm looking to find out...

1.) When does the 60-day clock start? Presumably at the point you leave the US? How is that documented (a receipt for some expenditure in the US just before you leave the country?)

2.) When does the 60-day clock stop (and reset)? Say I travel in Canada for 59 days, and then drive back across the border for the day to do some shopping or visit a doctor in the US and return to Canada that evening. Does this reset the 60-day clock? I'm thinking the best documentation here might be a record of the US doctor visit (which would be processed as any other claim in the US under medicare/medigap).

Anyone have some info or experience with this?

Thanks!

Dan