I assume that you are a homeowner, in which case you agreed to release equity at the end of your IVA or, failing that, extend for a year. This is that year.
As for the amounts involved, during an IVA you owe the full original debt, plus fees and possible statutory interest. Only at the end is anything unpaid written off.
On a £36k debt, very roughly, you would be looking at something like £7500 fees and disbursements and around £14k statutory interest, so payments would not stop until you reach the agreed term (including this extra year) or you have paid in about £57k.
If, during the year, you hit that figure the IVA will end at that point.
Now .... IF, as it sometimes is, statutory interest has been excluded (read through your proposal) the figure above would be reduced by around £14k, so, to pay back everything would only take £43k, in which case you might well have already done that. It is also possible, if the interest is not excluded, to petition the creditors to ask that it is.
Does that all make some sort of sense ?
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014