Ideally, the Voltage at a0 pin should be according to voltage divider rule.
(For the LDR circuit)
Then, if the high end voltage is 3.3 V and the low-end voltage is 0 V, the voltage at a0 pin should be between 0 and 3.3V.
However, I am getting readings which are much greater than 3.3V.
What do they signify? (Or is there some mistake in my circuit).
i appreciate your concern but A0 pin works under 0V to 1V. so for analog reading use that A0 pin. For digital you can use any of the GPIO pin from 0-4 which uses a power supply of 0V and 3.3V only.if you are getting higher reading then may be your circuit connection is wrong or you use GPIO pins instead of A0 pin where ADC reading happened. Make sure your connection is ok and also do share which project you are working on so that it would be easy to understand where is your doubt actually is.
The voltage at a0 pin is supposed to be between 0V and 3.3V for sure.
The only possible reason of getting a voltage greater than 3.3V at the a0 pin could be that you may have done the connections wrong i.e. the other end of the LDR may be connected to 5V pin instead of 3V3 resulting in the higher end voltage to be 5V.