540 person months is the upper limit for EU funding in MSCA-ITN and which may not be exceeded for ETN, EJD and EID proposals with a minimum of 3 beneficiaries, while 180 person months is the upper limit for EID proposals with two beneficiaries. If the proposal part B describes person months in excess of these upper limits, this should be indicated separately and be accompanied by a clear explanation of the use of own resources. Under no circumstances should the person months funded by own resources be indicated in the proposal part A (this would create confusion for the evaluators and at the very least result in an incorrect EU budget calculation, etc).
If a partner (non-beneficiary) finance the additional researchers this should be stated in the letter of commitment.