STM32G474RE ADC2 (PA1) Produces Unexpected ADC Readings

Hello,
I am currently trying to perform code generation on an STM32G474RE using a simple circuit model as shown in Fig. 1. However, when I attempt to read the output value from ADC2 channel 2 (PA1), the measured result shown in Fig. 2 is different from the expected result in Fig. 3.
I am not sure whether the ADC2 channel 2 (PA1) pin on my STM32 is damaged or if there is an error in my configuration. Could you help me identify the possible cause of this issue?

Fig 1. Simple Model

Fig 2. The Value of ADC in PA1


Fig 3. The Correct Value of ADC