For this to be same Richard Pearce snr there must be a typo on either the tombstone inscription (which clearly shows 7 Sep 1778) or the register transcript.

Jane, died 5 May 1780 according to the tombstone, does not seem to be in the parish record.

Graeme

as transcribed ?

Year 1780
Month May
Day 19
Surname PEARCE
Forenames Ann
Residence
Age at death
Officiating Minister
Event Burial
Cause of death
Memoranda
Notes
Register Reference P220 IN 1/1
Page No 135
Parish Chapel Mitcheldean