After-acquired clause

Could anyone explain the after-acquired clause to me? Or could someone view that if my explain is right, thank you!

In my opinion, after-acquired clause is a statement which can be used in the mortgage bond, for additional series of bonds with the same property or assets. For example, 10 asserts which can let us create 10 mortgage bond (one asset with one bond), and if the bond has an after-acquired clause, then, for example:

We get another 10 assets later, than these assets will automatically become the collateral of our bond, also, maybe there is a rule that in order to prevent the assets from being less valued, we must have more additional assets in our hands than additional assets used as collateral, for issuing additional bonds.
If we choose 60% for collateral and 40% in our hands, than the other 40% must be financed in order to get more assets in our hands (example:we put 5 million in the bank, after several month, may become 5.5 million), thus let us have more assets than before,(for example, if we get 10 assets later ,6 for collateral and 4 for assets, the other 4 must be financed at least to get to 6 in the end)at this time, including the first 10 assets, we have 16 assets for 16 mortgage bond, if we have more assets in our hands than being used as collateral (for example, after financing, 4 assets become 20 assets)after-acquired clause will let the issuer to finance unless it choose less than 43.75% for collateral, my calculation is listed as follows:
Suppose we now have 16 mortgage bond,4 additional assets, through financing, become to the number of 20 assets.
If assets in our hands equal the assets used as collateral:
1.we make 4 additional assets, 6 additional bond,
2.due financing, we get another 16 assets, than through step 1 , we successfully make 6 for 6, than we have 16-2=14 assets available, in order to get the equation, we can issue another 7 bonds
14-x=x, so x=7
Through these two after-acquired clause process, we can additional issue 6+7=13 bonds, then the action come to a balance state. Because additional assets in our hands equals the additional assets used as mortgages.If someone wants to finance, it maybe also permitted, in this situation, can but not must finance, through financing, thus have the probability to issue more bonds.(only from my point of view)
Another question is that if we get different assets than the original mortgage but as we need to issue a series of bonds whose mortgage is the same as the already-issued bonds, how will the collateral be changed?
Probably my expression will make you confused, but what l actually want to understand is:
What does the after-acquired clause mean?
Any example of the after-acquired clause?