If you want to understand the Pronto Hex IR format, I would start with the Classic Pronto Files section searching for User Documentation - specifically for a MS Word document by Barry Gordon entitled "Pronto Hex IR Format". There is another document there as well by Eigeny (Eugene) Elanov that may give you some additional information.

Also check out this:
[Link: remotecentral.com]

and this:

[Link: remotecentral.com]