Retrieving the os0 on0 information using API's

[charnwooduk]

Apologies if this post is to the wrong board

I have a paypal button which also passes optional "os0" and "on0" parameters. This is working as expected

<tr><td><input type="hidden" name="on0" value="plan"></td></tr>
<tr><td><input type="hidden" name="os0" value ="option_0"></td>
<tr><td><input type="hidden" name="on1" value="deviceID"></td></tr>
<tr><td><input type="hidden" name="os1" value ="abc-def-1234-1234"></td>

I can see this information in paypal as expected (see screenshot below, optional data is circled in RED)

My question is how do I retrieve this information back from paypal using automation? I have tested using RestAPI's, Webhooks, IPN but cannot see this specific data in any of the responses/messages

[jdisimon]

Using IPN these variables map to:

on0 ==> $_POST['option_name1']
os0 ==> $_POST['option_selection1']
on1 ==> $_POST['option_name2']
os1 ==> $_POST['option_selection2'])

Yes, strange mapping with the index offset by 1 (not to mention the names are different to begin with).