The researcher staff shall be seconded under the best conditions possible for the time of the exchange. Provided that this requirement is met, it is up to the beneficiary to manage the EU unit costs (no minimum per category).
As for the reporting, the REA will request the submission of the researcher declaration (RD) and the corresponding periodic report (According to article 19.1). You will not be requested to report on each category but the corresponding number of units (person- months) per researcher month per beneficiary.
In the case of an audit, each beneficiary shall keep proof of the time for the secondments (boarding pass, visas, etc…) as normal accounting practice.
(Answer provided by REA)