Here's an illustration from the service manual,sort of generic,but is probably right for all the 3 blade decks,hope you can tell something from it. You might get more information from the owners manual,go to Snapper.com/support/manuals,and use your exact model number,there are several different"LT16" models.
I'm sorry for the illustration again,It's hard to see. I checked the series 4 parts(still don't know which series mower you have)and there are 3 blades,and 2 belts,one "drive belt" P/N 7014801 A-92,and a "deck belt" P/N 7024497 AA-105,the "drive belt" comes off the clutch and through the "mule drive" then goes to the top pulley on the center spindle. There's one idler on the drive belt.The "deck belt" goes around all 3 spindles, the lower pulley on the center spindle,and 2 idler pulleys.