I can confirm the pelmet for your order is correct. We always leave the pelmet longer than the blind size ordered. This is to enable you to choose the perfect fit for your pelmet.
On our website there is a section about the pelmet size. This can be found on the ordering page, under the important notes section.
We do have a handy guide here on how to shorten a pelmet, just in case you need it: https://www.youtube.com/watch?v=rmXoDNLPDN8
Please note, when fitting inside of a recess you do not need to mitre the pelmet - this is only for an external fit. Therefore you can just do a straight saw with a hack saw.