Answer 1

In %6.3f, the 6 is the minimum number of characters to output and the 3 is the number of characters after the decimal point. Given:
float x = 123.56789
printing with %6.3f will output '123.568', while %10.5f outputs ' 123.56789'. Note that the first output required 7 characters so it outputted the extra one, while the second only needed 9 so it added a space.