Each lender has different ratios that they work with. For instance, if the BPO comes in at $180,000, they may be willing to accept $170,000 as they'd still be ahead of the game if they take the $170,000 and they don't have to pay for the cost of going through the foreclosure.
The fact that there's a lis pendens most likely only means that they started the foreclosure process as I believe in Florida foreclosures are started by filing an action in court and recording a lis pendens (in other states, including CA, most foreclosures are started by filing a notice of default). You should find out how far they have already gone in the foreclosure proceeding. If the bank wants to accept the short sale offer, the bank can postpone the foreclosure proceedings.
In summary, the bottom line is what the house is worth now, not how much is owed. Ask your agent to provide you with a comparative market analysis for this house. The CMA should also include some REO listings and sales. Best of luck to you.
If you're really looking for a home in Conway, I have one listed well below 199 and I truly love the area, and chose Conway on purpose, but my job i relocating me. here is the listing http://www.floridamoves.com/O4845680
good luck with your offer!