Hello! What you described is clearly not a serial connection. Maybe you write a model of the stove, maybe there is a diagram in the instructions. From the description, it looks more like circuits with contactors or burst switches.
In position 2 - they can and are connected in series, at least this is indicated by the fact that the voltage is different from 220. Logically, I will assume that the voltage is divided into three heating elements, and on each of them the multimeter shows 70 volts. Accordingly, the heating in position 2 is weaker than in position 3.
In the third position 220V on EACH heating element or on two combined? If on each, then the heating, most likely, is stronger than on position 2. They are connected in parallel without the third heating element.
And the scheme there is like this, only here there are 5 positions - 4 workers, organized through a packet switch, watch the right side. Where the point is, the chain from the arrow to the heating elements is closed. In zero, everything is off, in the first position two chains of 2 heating elements in series, in position 2 only the upper ones, in position 3 only the lower ones (perhaps they create more temperature, because the heat rises upward) in position 4 - everything is included parallel. So you have this type.
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