I think grinders in this price bracket can often have some sort of restraining component to prevent the burrs from getting too close. If you open up the grinder (if that is even possible!) and have a look you might be able to remove it. Years ago when I was starting to get into coffee I had a £70 Dualit grinder and I vaguely recall dismantling it and removing some sort of component which then enabled it to grind much finer- I realise not very specific but we are talking 10 plus years ago now. I then recall trying to take apart my Delonghi filter baskets to try to make them non pressurised-with limited success as I seem to recall!