This is the 10457th most frequent Spanish word.
contarlo
"Contarlo" means "to tell it" or "to count it" in English.
Here, 'contarlo' refers to the act of recounting or narrating a story or incident, with 'lo' being the direct object.
No puedo contarlo sin emocionarme.
I can't tell it without getting emotional.
In this case, 'contarlo' is used to mean 'share' or 'relay' information, again with 'lo' as the object.
Si me lo dices, puedo contarlo a las personas interesadas.
If you tell me, I can share it with the interested people.
Here, 'contarlo' is used in its other meaning, 'count' or 'calculate,' indicating an enumeration or computation task.