What does 1 decimal place mean?

Answer 1

For a number such as 347.213 it means ignoring all places to the right of the decimal point except the first - hence 347.2

However if the next number (in this case the second number after the point, is 5 or more, then it is more accurate to advance the first number by 1. So 347.263 would be quoted as 347.3, simply because that is closer to the original than 347.2

This business is called "rounding to 1 decimal place", or simply "rounding"