Envolep and A4 paper stock

What is the Company's Main business?, I mean does it sells envelopes & Paper?

If no, then it should be charged to PnL as Printing & Stationary expenses. in such case,  you will not be required to report consumption of it any where in financials.

However for your own internal control purpose you can derive the estimated consumptions based on budgeted Sales / Target sales for that specific period. Past trends can also help in this regards.