How is allocated or committed stock taken into account?

StockTrim does not explicitly take allocated stock into account (also called committed stock), but general best practice is to not include this in your Stock on Hand. Ideally the Stock on Hand should be your available stock (on hand minus allocated), since this is the amount you have to meet future demand. Obviously, allocated stock can not be used for future demand since it is already assigned to be used.

If your Inventory Management System has an available stock field, then StockTrim will sync with this by default (which is on hand minus available). However if you want to sync with the on hand field only, then this will be a configurable setting under Settings -> Features. 

For Unleashed and Cin7 users, StockTrim will sync with the Available field for Stock on Hand by default (unless you enable the "use stock on hand instead of available" setting. 

For Katana users, StockTrim's on hand field will, by default, be the Katana on hand amount, minus committed stock. If you wish to include only the Stock on Hand value, enable the "include allocated stock in on hand values" setting.