All bullion in storage is audited on real time basis. Additionally, all incoming and outgoing bullion is monitored with the full oversight of local customs authorities. Physical available bullion balance is reflected real time in your account.
Related articles:
Where are my bullion physically stored?
http://help.stackermarket.com/en/articles/5355736-where-are-my-bullion-physically-stored
What is the fee for storage per year?
http://help.stackermarket.com/en/articles/5355737-what-is-the-fee-for-storage-per-year
Can I visit my bullion and withdraw in person?
http://help.stackermarket.com/en/articles/5355747-can-i-visit-my-bullion-and-withdraw-in-person
Are my bullion holdings fully insured?http://help.stackermarket.com/en/articles/5355742-are-my-bullion-holdings-fully-insured