this is the christening i found so doesnt make sense
No, it doesn't.
The obvious conclusion (assuming that Ancestry's transcription is correct - you need to look at the original document at
www.scotlandspeople.gov.uk to check that) is that were two couples with the same names.
Another possibility is that the parish clerk, when writing down the details, didn't realise that this was an adult baptism, and/or forgot to write down the actual year of birth.
I've been trying to find Charles F, wife Mary and daughter Margaret in 1841, so far without success.
However there is a possible Margaret Finlay, aged 14, in the household of George Duncan, spirit merchant, in Airdrie in 1841. The only problem is that this gives her county of birth as Lanarkshire, not Renfrewshire. On the other hand, this too could be an error.
There's also a 15-year-old Margaret F in Moodiesburn, parish of Cadder, in the household of Charles F, (transcribed as L but should probably be I for Iron) miner, aged 40. The problem with this is (a) her birthplace, again, is Lanarkshire and (b) if this is her, you need to explain why there are no baptisms of what look like two brothers and two sisters. On the other hand, it fits with her marrying the following year in Cadder.