It's an open brain coral. It's tissue is retracting in the lower right. I would dip it in an attempt to remove any parasites that might be present.
Lower light especially during acclimation & recovery. Steady flow is OK but avoid direct, strong laminar flow. Feed it whene ear it is ready.
The bottom is the right place for it, but maybe try elevating it directly off the sand. I have a personal theory that sand can be a vector for nasties for stressed corals in some cases.
If the tissue continues to retract, I'd dip it again & treat the exposed skeleton with a drop of hydrogen peroxide, dip the area clean in SW, add a drop of concentrated iodine (avoid getting on healthy tissue) & maybe a drop of anti bacterial compound. Rinse between each compound & keep the healthy polyps wet & don't take too much time. Caution: I cooked up this procedure myself & saved 2 scolys & an Aussie war coral this way. It's not a common treatment so use only as a last resort & at your own risk. I've read of people cutting away the exposed skeleton or fragging a remaining healthy polyp if it looks to be going downhill fast. Never done this myself but maybe others can advise on this.
Don't know your experience level, but its a stony coral of course so you need the right levels of calcium, alkalinity & magnesium...nothing else matters if you don't have that part right. If you can stabilize this piece then you'll have a heck of a bargain for ten bucks. Good luck.