What does R.S., 1985, c. 30 (4th Supp.) means in Canadian law?

I have to translate a Canadian Act: Mutual Legal Assistance in Criminal Matters Act R.S.,1985, c 30 (4th Supp). From what I understand "R.S.,1985, c 30 (4th Supp)" is like a reference but what I don't understand is that why after that it says " [1988, c 37, assented to 28 July, 1988]? What happens with the year 1988? Or chapter 37? And why "assented to 28 July 1988" while the reference after the title of the Act is R,S, 1985.....? That means it became an Act in 1988 but it was published in the RS in 1985? And what is a Supplement exactly? Anyone who knows about this, please help. I am so desperate.

What does R.S., 1985, c. 30 (4th Supp.) means in Canadian law?
It mean is was a 1988 Act which was supplement by the 1985 revision act which suppose to add on, change or delete something from the 1988 Act

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