A few questions about electric field and equipotential lines of parallel plates with widening ends

I’m a second grade physics student and I take Electricity and Magnetism course and I have laboratory class. Due to pandemic I can’t go to laboratory and find out the answers of my questions by using the equipments in my university so I need to use internet and research about my questions. Unfortunately I couldn’t find enough information on internet about my questions so I’m here asking my questions.

I was doing a lab experiment about parallel plates in 2 dimension but the plates are not straight at all.

You can see the circuit of the lab experiment on the above diagram. Distance between plates is $a=8cm$ and length of straight part of each plate is $b=10cm$.

On the next image, you can see the teledeltos paper used in lab experiment circuit. We painted our parallel plates using silver paint. We give $V_0=9V$ of voltage using our D.C. power supply.

We calculated the electrical potential difference of each dot in on the milimetric paper using voltmetre and noted next to each dot as in the following image. Each dot is seperated with $1cm$ distances.

We only used voltage values of points on the middle line ($V_1$) and the line $1cm$ above the middle line ($V_2$). Using these values I filled the table below.

My questions

1. How electric field is created using this circuit? We connect tip of each plate to our circuit using conducting wires and thus there is a current on plates but I can not understand what is happening behind the scene when we set our D.C. power supply to 9V. Could u explain how does the electric field created?

2. Magnitude of the electic field created by parallel plates is calculated using $E=frac{V_0}{a}=frac{9V}{0,08m}=112,5 V/m$. We drawed equipotential lines with 1cm distance between each of them. So we can calculate the electrical potential difference between each equipotential line using $Delta V=EDelta z=112,5 V/mcdot 0,01m=1,125V$. But if we consider the $Delta V$ values calcuted on the expiermental circuted the valeus of $Delta V$ varies between $0,3V$ and $0,1V$ which is not close to $1,125V$. Could you explain me why there is a difference like that?

3. What does the total of $Sigma E_{ort}Delta y$ values on the last column tell us about? (ort. means avg. by the way) This total value has some relation with experiment background information.

My lecturer in lab told me that the total of last column values ($EDelta y$) in range of $y=[0cm, 10cm]$ should equal to $Phi=int{E_z dy}=V_0left(frac{b}{a}right)=9Vfrac{0,10m}{0,08m}11,25V$. What does this value mean?

Thanks!