Нашёл:
Total spend is a tally of all the money you spent on Steam, whether that’s buying games for yourself, gifting them to others, or buying anything off the Steam Market.
Сколько всего потрачено на покупки, подарки, на безделушки на торговой площадке.
Old spend only shows the money spent up before April 17, 2015. You may remember that Valve instated a policy around that time that restricts users who have not spent at least $5 from trading, sending friend invites, or using the market.
Сколько потратил до 17.04.2017, тогда Стим ограничил возможность торговли на маркете юзерам, потратившим менее $5 на покупки.
As for PW spend, it’ll simply track all the money you spent through a Perfect World account in Dota 2, or Counter-Strike: Global Offensive. For anyone outside of China, this will most likely be $0, since it only tracks the Chinese versions of those games, which are co-published in the country by Perfect World.
Сколько потрачено в перечисленных играх, но только для юзеров региона Китай (думаю, так сказать будет правильнее), остальных он просто не считает.