Hi,
You might want to check the wikipedia 10 article about float numbers.
The short answer is that single precision float have up to 6/7 digits of precision. Anything after that is noise.
So here 1 - your_number < 1e-6 means that from the point of view of single precision floats, they are the exact same number. You won’t be able to get more precision with them.
If you needs more precision, you can use double precision floats that will give you ~12 digits of precision.