What does the number in parentheses of X-ray data mean?

Here for example: xyz coordinate for Ir-atom that is included in Ir-complex. The first question: what does  the bold number in the parentheses mean? Ir1 Ir 0.18461(3) 0.28575(3) 0.160923(15)...

07 March 2017 3,199 6 View