How to fix 60g liquid output from 18g shot.

Hi everyone I was hoping for some advice, I have been getting 60g out from a 18g shot using the finest setting in my eureka Mignon. It takes about 23 seconds. From my understanding I need to grind finer since I probably get around 36g out after a 15 sec pull. However I’m already using the finest grind setting. Any suggestions?