Notation for specifying the fractional part of a number
The fractional part of a number $x$ is usually denoted by $\{x\}$ or $\operatorname{frac}(x)$ (see Wikipedia), i.e. $\{x\}=x-\lfloor x\rfloor$, where $\lfloor \cdot\rfloor$ is the floor function.
Braces is a common notation so the fractional part of $x$ would be denoted by $\{x\}$.
That being said, I would rather not use it without explaining it.