I suspect there is a better way of expressing this:
A point $p$ that is in an interval around a point $o$, the interval extends in both directions by a constant $c$.
$o - c < p < o + c$
or
$\left|p-o\right| < c$
I think it would be far more clear to express this as "$p$ in $o \pm c$", how would I write that?