Hisense I6433CB7 Detailed Instructions page 30

Any changes to the sheen of the graphic design elements or discolouration should not
be deemed as damage to the appliance, but rather a result of normal use of the cooking
hob. Such discolouration is most commonly a result of food residues burnt onto the
surface, or it may be caused by some cookware materials (such as aluminium or copper).
Such discolouration is very difficult to remove entirely.
Note: Discolouration and similar flaws only affect the appearance of the hob and do not
directly affect its function. Removing such flaws shall not be covered by the warranty.
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Hold the scraper at the correct angle (45° to 60°). Gently press
the scraper against the glass and slide it over the signage to
remove the dirt. Make sure the plastic handle of the scraper (in
some models) does not come into contact with a hot cooking
zone.
Do not press the scraper perpendicularly against the glass
and do not scratch the hob surface with its tip or blade.
Immediately remove any sugar or sugar-laden food from the glass
ceramic hob using a scraper, even if the hob is still hot, as sugar
may permanently damage the glass ceramic surface.