petition receipt number: your previous H1 approval notice number (I-797) so you don't claim a new quota number.
prior,..., in your case, it means the number of the same notice. (unless you have another COS pending to fill the gap, then it is the number of that other notice)
your action is EOS, if it is H1 transfer. Unless it is H1-other-H1 but using the first H1's quota. Then you should check COS.