Oh I see what you mean. So next to selectall, You need a numberbox like `Select Quantity`, and if 17 entered and press enter, you want 17 assets to be selected?  Interesting, wonder if many are running in this usecase. Unless you frequently perform some bulk asset operations. Will wait to hear what ...

This comes OOTB on AEMCaaS : The screenshot you added is classicUI whose support is stopped. If you switch to TouchUI, you have the feature you are looking for.