The annotations were made by the census clerks (not supervisors) when extracting data. On the pages of the original books these marks are in coloured inks, crayon or pencil, and can be easily differentiated from the enumerators' returns. On monochrome microfilm these additions are difficult to differentiate.
As far as the GRO was concerned the enumerators' books were merely the raw material for the production of the 'Census Reports.'
Stan