In 1841, ages over 20 were supposed to be rounded. 25 could mean 25, 26, 27, 28 or 29. It could also mean 24, as some people said they were 25 when we would say they were "in their 25th year".
From another site:
Welltrees Square, Maybole 1841:
Archibald Clyde, "35" cotton hand loom weaver
Mary Clyde, "30"
James Clyde, 18, apprentice cotton hand loom weaver
Archibald Clyde, 11, apprentice cotton hand loom weaver
Isabella Clyde, 14, cotton land loom weaver
John Clyde, 9
Neil Clyde,5
All are born in Ireland
At Ladyland Street, Maybole, in 1851:
Archibald Clyde, 52, cotton hand loom weaver, b Ireland
Mary Clyde, 50, cotton winder, b Ireland
Isabella, 24, hand loom weaver, b Ireland
Archibald Clyde, 22, cotton hand loom weaver, b Ireland
John Clyde, 19, cotton hand loom weaver, b Glasgow
Neil Clyde, 16, cotton hand loom weaver, b Ireland
Archibald Clyde, 6, grandson, at school, b Maybole
Margaret Meechin, 14, general servant, b Grvan, Ayrshire
Archibald, aged 6, was the son of James and Elizabeth Clyde, who also live in Ladyland Street:
James Clyde, 27, cotton hand loom weaver, b Ireland
Elizabeth Clyde, 27, cotton hand loom weaver, b Girvan, Ayrshire
Mary Clyde, 1, b Glasgow.
In 1861, James and Elizabeth Clyde are in Great Eastern Road, Glasgow, with Archibald, 17, b Maybole, Mary, 11, b Glasgow, James, 9, b Glasgow, John, 7, b Glasgow, Jane, 1, b Glasgow.