There is only 10 oz of gold in the example. If you really think that 15 oz actually exist, I'd say you've got some cognitive challenges.
Rather, they book both the deposit & asset out of thin air when the loan is made, then go shopping for the incremental reserve. Even better, the reserve itself is typically phantom as well. (Especially if they are a Fed member which has reserves already sitting there that were themselves conjured out of thin air.)
A truly beautiful zero bound system; the only restriction is **confidence**. That's why all efforts have been directed towards re-igniting lending. The game must continue, or all is lost (for them anyway).