In this section

Historical Rules · 25 September 2014

Rule 121.6

Official source text from the 25 September 2014 Rules release

Some spells and abilities refer to counters being “placed” on an object. This refers to putting counters on that object while it’s on the battlefield and also to an object entering the battlefield with counters on it as a result of a replacement effect (see rule 614.1c).

Find this number in the current Rules