What does dualy affixing a postal stamp means.....?

So here is my problem....I am trying to fill an application form which is asking me to duly affix postal Stamps on 2 envelopes each of 22/- rs each.So should I affix 2 postal stamps on each I.e. total will be 4 or 1-1 each on the envelopes I.e. total 2.....I am confused due to duly affix of postal stamps.....my other questions are....
1. What does 'P.S.' mean under permanent address section and what to fill ?
2. What does 'Post'mean under permanent address section and what to fill ?
Please please reply fast....asap

?2015-02-06T02:24:27Z

Duly is meaningless in this instruction. Just stick the stamps on in the right place.