I just updated the map data for Park Prirode Lastovo. According to the information on their site, they currently have 57 Buoys for boats up to 20 meters, located on the following 4 places:
On the site of the PP Lastovo, they speak of "mooring in a row", meaning that each boat should use two buoys: One buoy at the bow and the other one at the heck of the boat. Finally this should build a row of boats (eg 3 boats use 4 buoys). In reality this is not always possible...
Detailed information about pricing can be found on the site of the PP Lastovo (see here).