EC is for "as collected", so pretty self-explaining isn't it?
P.S. This is a typical question for the LinkedIn "SDTM exp erts" forum https://www.linkedin.com/groups/2758697/ which has over 3,200 users ...
Use the ECMOOD variable. ECMOOD = SCHEDULED and then ECMOOD = PERFORMED.
Take a look at section 6.1.3.2 in SDTMIG-3.4 for examples.
The planned dose frequency(BID) and actual dose frequency(QD) are different. How to represent this record in the EC domain?