:5d|9d|16d|28d

Is how to put four single commands in a row. But better turn it around:

:28d|16d|9d|5d

To keep the numbering constant.

:5d|9d|16d|28d

Is how to put four single commands in a row. But better turn it around:

:28d|16d|9d|5d

To keep the numbering constant.

A more flexible way is to use vimscript. Squeezed on one line this is:

:for n in [28,16,9,5] | call deletebufline("%",n,n) | endfor