Why is M53 motorway showing 50mph speed limit southbound and 70 mph northbound'

MallyGo

M53 is shown as having 50mph speed limit southbound between junction 10 and where the motorway becomes the A55 when clearly it should be 70mph, Speed limit reverts to 70mph at this point. Northbound on the same part the the road is OK.
Also why are so many 20mph limits shown as 30mph. Given that this is one of the latest sat navs, one could suspect that it is not fit for purpose

MyNameAllreadyExists

See: https://www.legislation.gov.uk/uksi/2006/2912/regulation/2/made

And: https://www.legislation.gov.uk/uksi/2006/2912/pdfs/uksiem_20062912_en.pdf

This instrument imposes a permanent 50 miles per hour speed limit on a 560 metres length of the M53 Motorway and on the entry and exit slip roads leading from and to the A5139, all at Junction 1 of the M53 Motorway on the Bidston Moss Viaduct in the Borough of Wirral in the County of Merseyside. This permanent speed limit is being imposed in order to improve road safety.

MallyGo

Please engage brain before giving an answer. The question refers to Junction 10 ( ie TEN) not junction 1