docs: add information about precision and exactness

closes #1273

docs/user/basics/intro.md

@@ -39,5 +39,6 @@ Concrete is a work in progress, and is currently limited to a certain number of
 The main _current_ limits are:
 - **Concrete** only supports unsigned integers
 - **Concrete** needs the integer to be less than 7 bits (included)
+- **Concrete** computations are exact (except a very small probability) for computations on 6 bits or less, and exact at a probability close to 90% for 7 bits computations
 
 To overcome the above limitations, Concrete has a [popular quantization](../explanation/quantization.md) method built in the framework that allows map floating point values to integers. We can [use this approach](../howto/use_quantization.md) to run models in FHE. Lastly, we give hints to the user on how to [reduce the precision](../howto/reduce_needed_precision.md) of a model to make it work in Concrete.

docs/user/explanation/fhe_and_framework_limits.md

@@ -28,4 +28,7 @@ As of today, the execution of the FHE program is done locally. Notably, in the c
 
 As we explained, we wanted to focus first on cryptographic challenges. Performance has been postponed, and will be tackled in the next release.
 
+### Currently restricted to 7 bits computations
+
+For the moment, we can only perform computations with 7 bits or less. Furthermore, the exactness of computations is only ensured for 6 bits or less; for 7 bits, the computations are exact with a probability close to 90%. Of course, we are working on increasing this limit, and making the probability of a wrong computation as close to 0% as possible. Don't hesitate to look at our [quantization](quantization.md) section to know how to use smaller integers.