As the others have said 1/300 is considered risky. Mine came in at 1/37 for DS mainly because of a 4.2mm NT measurement but also due to my age (42). My bub was born without DS.

The hard bit about these non invasive tests is they can't really tell you anything. Women who come in as low risk can still have DS babies. The only way you can know for sure is to have an amnio or CVS and with a result like yours it's unlikely to be recommended.