Metrohm 827 pH lab - Manual (Page 49)

7 Various functions
826/827 pH meter, Instructions for Use
41
Measured value no. No. of stored measured values
You can now use the two arrow keys <> and <> to leaf between
the measured values.
In order to delete all measured values select the second parameter
del mv store: in the above measured values memory menu and set it
to 'yes' with <>; then confirm this and the following safety query
delete ? with <OK>.
Note!
It is not possible to delete just individual measured values out of the
measured values memory.