Actually I suggest you check the country specific requirements for Sri Lanka. And if it does not say for last ten years, I would also suggest contacting IRCC through webform and asking, and likely in parallel getting the since-age-18 police record from authorities.
I believe almost always they are asking for police certificate (criminal record check really) since 18 (or whatever "age of majority" is in each country. Remember, they're not just interested in crimes you may have committed in last ten years but full police record (some crimes even long ago would make you inadmissable).
While it's hopefully unlikely that they'd send it back because you submitted the ten year form, it's possible, and it would be a shame if they sent it back because of this. Espeically if you submitted in March, you'd lose a lot of time.
If you contact them it's more likely they'd give you a chance to provide the certificate.