I don't know that there's any definitive, publicly-available information on this, but I recall from the last time I applied (when I was chosen as a finalist for an ETA but ultimately not selected) that the common knowledge seemed to be that around 2x as many people were selected as finalists as those that were eventually awarded the grants for each specific program. So that means if there are 25 ETA spots and 10 full research grants for a country, around 50 people will be chosen as ETA program finalists and 20 as finalists for research fellowships.