I'd agree it does say 'Tunstill', but I can't find anywhere with that name in Cheshire.
There is a 'Tunstall" in North Staffordshire, not many miles east of the Cheshire border - about 30 miles to Chester itself.
Perhaps she was unsure of the county, or the enumerator didn't bother to check.
Unfortunately you have put the red box through the birth place given for her daughter, so we can't factor that clue into the question - does it say 'St Mary's', the same as her granddaughter?
Intriguing that her grandson was born 'over the seas', and is a BS (British Subject).
For future reference, there is no need to highlight a word or words you need help with. Just an explanation of which ones would suffice. As I say, it does mean a loss of possible clues that might help.
It only rang a bell with me as I had ancestors in Cheshire for many generations, then lost them, eventually finding they had originally hopped north over the Cheshire border from Tunstall in Staffordshire.