GE JP3021DPBB Owner's Manual And Installation Instructions page 7

Surface Elements (Cont.)
Dual Surface Element (on some models)
The left front surface element has 2 cooking sizes to
select from so you can match the size of the element to
the size of the cookware you are using.
To use the large surface element, turn the SELECTOR
knob to
desired setting. The element will heat the entire area
contained by the larger circle.
To use the small surface element, turn the SELECTOR
knob to
setting. The element will only heat the area inside the
smaller circle.
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Surface Elements Cycle On and Off
Surface elements will cycle on and off to maintain the
temperature you have selected.
All radiant surface elements have a temperature limiter
that protects the glass cooktop from getting too hot.
The temperature limiter may cycle the elements off while
cooking if:
The pan boils dry.
The pan bottom is not flat.
The pan is off-center.
There is no pan on the element.