I can see Volume 11 not age 11 on Ancestry....

Name: Sophia Barnett
Year of Registration: 1850
Quarter of Registration: Oct-Nov-Dec
District: Westbury On Severn
County: Gloucestershire
Volume: 11
Page: 372

FreeBMD says :-

Surname First name(s) Age District Vol Page
-------------------------------------------------------------
Deaths Dec 1850 (>99%)
------------------------------------------------------------
BARNETT Sophia Westbury on Severn 11 372

and I'm "sure" no corresponding BENNETT, so I think our transcription may also be the right one for Sophia.