I understand the basic difference between less and fewer: you use "less" for things that aren't counted (There is less water in the pool than yesterday; I feel less hungry now than before).  You use "fewer" for things that are counted (There are fewer than eight cars in my garage; There are fewer jellybeans in that jar than you think).

What if what you're describing IS countable but you don't mean a full unit less?  For example.... if I said, "There are fewer than two gallons of water in that jug" this suggests that there are 0 or 1 gallons.  But what if the amount is 1.9 gallons?  There aren't really "fewer" than 2 gallons, since rounded off 1.9 is 2 anyway, but there Is "less" than 2 gallons in there... right?  The same can go with something like time.  People say "there is less than one minute left" even though minutes can be counted.  So, should I say "There are less than two minutes left" if, say, 1 minute and 57 seconds is left?  Or am I just crazy?

Thanks for your help.