From the tests I did I could notice these constants:

1. The healthy leaves gave NDVI values between 0.2 and 0.35;
2. The semi-dry leaf gave NDVI values between 0.4 and 0.5 in its green area; and
3. The dried leaves gave NDVI values between 0.66 and 0.75 approx.

Recommendations to build the AS7263 sensor module: 

1. It's not necessary to add any additional light source since the LED that the module itself has is sufficient;
2. It's necessary to place a holder for the leaves so that they are at a constant distance from the sensor (5mm); and 
3. We must do the tests in a room where the light is constant, it is not recommended to do the tests outdoors due to the strong solar radiation.

The tests carried out were satisfactory, and it was a good experience to learn new things such as: 

1. I discovered that the leaves of the plants give NDVI values according to the type of plant analyzed, since the green leaves of plant 1 gave me approx. NDVI values of 0.2, and plant 2 gave me approx NDVI values of 0.3; and 
2. When I did tests with a semi-dry leaf, I discovered that it gave approximately NDVI values of 0.5 in its green part and 0.73 in its dry part.