It seems we have different results.
I checked the 1841 CEN census and it said Cathren was 7 years old, consistent with her 1834 birthdate.
I checked the actual passenger log of the bounty ship "Margaret" date on ledger is 24 January. The ship left Greenock Scotland on 6/10/41. George Munro is listed as an agricultural labourer aged 35, native of Edinburgh, could read and write and religion as Church of Scotland.Father Daniel soldier (dead) mother Jane (dead). Wife Mary Munro age 34 native of Isle of Bute.
Reel AONSW1345 shows George Munro had a contract with D Riddle to be paid 30 pounds a year with rations. The contract was for one year.
A search of the NSW historical register of births showed George Munro and Mary Thompson Munro as parents of a daughter Mary Jane Munro,(yes it actually says Jane) who was born at Bowenfels NSW in 1843. I matched the maiden name Thompson given in the NSW birth registration, with marriage records of several George Munro's either side of 1834 in Scotlands People website and found that on 15/06/1833, a George Munro had married a Mary Thompson in Gorbals, Lanarkshire. Given that the immigration records stated wife Mary as a native of Bute and the NSW birth register gave her maiden name as Thompson, it seems likely that Cathrine's mother was indeed Mary Thompson, native of Bute.
Further search of parish records for Edinburgh revealed that 0n 18th Feb 1807, a Daniel Munro and Jane Graham had a son named George Munro. The bounty records state that parents of George Munro were Daniel Munro and Jane Graham.
Daniel Munro was the son of a William Munro and Margaret McDonald born 26 October High Kirk parish. Edinburgh City Archives revealed a William Munro, native of Rosskeen, Ross & Cromarty, was enlisted in the Edinburgh City Guard on 12 June 1789.
Since beginning this quest for knowledge of my ancestors, I have discovered there often are small inconsistencies in spelling etc and also ages recorded. I think this is more consistent with varying levels of literacy etc.
I also endeavour to cross reference as much as possible, using when possible the original source rather than ancestry sources.