This is the maximum limit of your shop inventory items, including items from all Steam games, Steam community items and Steam gifts. VIP can apply Backpack Expander to increase this limit (up to a maximum of 2000). Every donation of $0.6 beyond $50 also increases the limit of Steam community items and Steam gifts by 100. Note that the effect of BP expander and extra donation does not stack. The one that precedes the limit is taken into account.