Assuming the brushhog is correct for the tractor with respect to the direction of PTO rotation (some especially earlier Kubotas have a 'backwards' PTO direction of rotation) you'll find that the 'hog will tend to throw cuttings out the rear but more to one side----much like the deflector on a pushmower points to one side.
Pay attention as you drive slowly and you should see a definite pattern. Then you decide if you want to throw cuttings to the already-cut side for ease of operation or toward the to-be-cut side in order to recut and mulch. "Right" direction is eye of user based on desired outcome.
Bushhog being not a precision machine don't expect miracles.
I painted on deck of mine the more prevalent "discharge direction" as a reminder when trying to get best possible cut.
Some bushhogs rotate their blades one way, some another, all regardless of PTO. Check at a large supplier and you can find hundreds of blade types. If not careful you can get a blade just like yours with same hole, angles, wings, length, width, but with the cutting edge on the wrong side.
If you have doubts for any reason (previous owner or other well-intended party) contact manufacturer for part number and diagram of what your blade SHOULD look like and compare.
I've seen blades mounted upside down, backwards, too short, trimmed with torch, sharpened incorrectly, attached with plain bolts not keyed, 'correct' but cutting edge backwards for rotation. Have become very suspicious of bargain brushhogs.
Believe it or not blades bend fairly easily and last year managed to break one. That was exciting for a few seconds. Blade life depends on use. When you have them off to sharpen compare one to another or to a new set that you keep on hand for spares and you'll see deformation over time.
Depending on intended use and your machine I suggest a disk-type stump-jumper instead of a bar for mounting blades. Get a bar-type wrapped up around a sapling and it'll turn the tractor sideways in a heartbeat--or stall or break something.
Get proper wrench for nut and remove blades annually or as needed to put in vise and sharpen with hand-grinder. Use new lockwashers each time. Watch the key on the bolt for wear. Thread sealant on bolt will allow easier future removal.
Check gearbox frequently while new until seals wear-in and top off with mfg's suggested gear oil type.