This is a sum of external funds that have been applied to your Steam account, either to purchase games on the Steam store or fund your Steam Wallet. These values are calculated only when needed and are not always current. If the values are not presented below, they are not currently stored in our database but you can always find a full list of your purchases at
https://store.steampowered.com/account/history. "TotalSpend" is the total amount of external funds applied to your account. This value is used to determine if an account is a "Limited User Account". "OldSpend" is the amount of external funds applied before Friday, April 17, 2015 18:00:00 UTC. If your account was linked to Perfect World for CS:GO or Dota 2, "PWSpend" will be the approximate USD value of funds applied from Perfect World, otherwise that value will be zero.