Anne Bronte's grave

I visited Anne Bronte's grave this morning at St. Mary's churchyard near Scarborough Castle.
Anne Bronte (1820 - 1849) was one of three literary sisters from Haworth and she wrote 'Agnes Grey' 1847 and 'The Tenant of Wildfell Hall' 1848.
Charlotte Bronte wrote 'Jane Eyre' and Emily Bronte wrote 'Wuthering Heights'.
Ann developed consumption and whilst staying in Scarborough she died aged just 29.
The grave marker erroneously reports her age as just 28.