Understanding a chemical reaction from kegg
The $n$ of the polyphosphate should be decreased by 1 on the reactant side relative to the product side:

$\ce{(P)_{n} + Glc -&gt; G 6P + (P)_{n-1} }$

Polyphosphate, like ATP, contains several phosphoanhydride bonds.  These are "high energy" bonds that can be used for biosynthesis.  But to do so one of these bonds needs to be broken, and that is exactly what happens when one of the end phosphates on the phosphoanhydride chain is peeled off and trasferred to glucose.