Please see this verse which says that Goddess Sita resided in Ayodhya for 12 years before she left with Lord Ram and Lakshman http://www.valmikiramayan.net/utf8/aranya/sarga47/aranyasans47.htm#Verse4
But then see verses later it is mentioned that Lord Ram's age at time of exile was 25 years and Goddess Sita was 18 years. http://www.valmikiramayan.net/utf8/aranya/sarga47/aranyasans47.htm#Verse10
This doesn't make sense as Lord Ram cannot 13 when he got married . Is there some error in translation ?