What's this line mean?

“A BUSHEL—THAT’S FOUR WHOLE PECKS—OF THANKS TO…” form a book. i am not an native english speaker,so i don’t know what’s the meaning.expect someone can help me.thank you

Those are units of measure. AFAIK not much used except for farm produce. Somewhat similar to saying
A liter - That’s 10 whole deciliters - of …
except a bushel is a basket size

I’m guessing you didn’t mention the context very well and it’s a pun on the work “peck” used for a “quick kiss”?

I think it’s just a way of expressing “many thanks”.

Bushel and Peck are units of volume.

In the US system:

1 bushel = 35.24 litres

1 peck = 8.809768 litres

thanks guys ,got it.