The “15 to 17” part is worded somewhat confusingly, but it’s not wrong.
The number of bits contained in a double is equivalent to ~15.95 decimal digits. If you want to store exactly a decimal number with a fixed number of significant digits, floor(15.95) = 15 digits is the most you can hope for. However, if you want to store exactly a double by writing it out as a decimal number, you need 17 digits.
I’m not sure where the 17 comes from. It’s 15.
The “15 to 17” part is worded somewhat confusingly, but it’s not wrong.
The number of bits contained in a double is equivalent to ~15.95 decimal digits. If you want to store exactly a decimal number with a fixed number of significant digits,
floor(15.95) = 15digits is the most you can hope for. However, if you want to store exactly a double by writing it out as a decimal number, you need 17 digits.