The instructions for entering relatives from the 1841 Census include this warning:
Note: the references in the transcription may be incomplete, or even wrong (at Ancestry); see the FAQs page for an explanation of how to interpret the references shown in the census image. When a private household is split over two pages use the references for the first page for the entire household.
Anyone who uses Ancestry's 1841 Census references without checking them can miss out on matches, which is why this warning appears every time you enter (or edit) someone from the 1841 Census; in the case of Lawson Dunn the correct census references are 298/6/8/10 and in accordance with the instructions on the form the same references should be used for the entire household.
I always take the 1841 references from the handwritten census form - it only takes a few seconds longer, and it eliminates the possibility of error.
Be careful using findmypast - if the household you search for is split over two pages, and the individual you search for is on the second page, the census references displayed will relate to the second page. This is another reason to take the references from the image, rather than the transcription.