To get your result, try something like this.
String key = "Losses";
int value = 0;
Query query = QueryBuilder.Build(key, value, Operator.EQUALS);
storageService.FindDocumentsByQuery(dbName,collectionName,query, new UnityCallBack());
For Update
Query query = QueryBuilder.Build("Losses", 0, Operator.EQUALS);
storageService.UpdateDocumentByQuery(dbName, collectionName, query , "{\"Losses\":1000}", new UnityCallBack());