Tires, I don't understand them

Yesterday I was in the field mowing hay. It was going fairly well until I got to the last big piece. As I turned the corner my tractor started doing this very loud womp

Womp. Was I Chogged up? Nope. I had a flat that busted through the sidewalls of the tire. 

Called & texted DH & headed to the house to get the other Tractor & swather. 

Once DH got home he got his tools & started getting that tire off the rim. I'm thankful that the rim want damaged. This next pic you can kinda see the tractor without it's tire. 

He put the tire into the loader arms of my tractor & I hauled it home. 

This morning I spent chasing down a tire. I think I found one in Falls City NB. It's about 1.5 hours from home. I've never understood tire measurements. DH has tried to explain them to me but it hasn't stuck. 

I'd better get back at it. In sure that the hay is ready to bale. I'll get back to sewing hopefully soon. More later on,

Vicky