If you've bought an in-expensive one, you may not have this info.
Tried to post both Pics from Camera, and Scans, and neither would post clearly enough, so here goes.

Water should not be left in Oven bowl after washing action is completed, as condensation forms inside the cooktop causing it to deteriorate over time. Condensation can lead also to earth leakage problems which can be very irritating when modern super-sensitive earth leakage protective devices turn your power off.

Food should not be left in the oven once the unit has ceased cooking- the food can spoil and moisture will condense in the cooktop and cause deterioration and in particular may cause a very small earth leakage.[See above].
Cheers,
xina.