only 4 cores

I bought an intel i5 9400f. My old CPU was an i3 8100. My pc says that I have 6 cores, but my windows sees it as 4 cores. I looked at device manager it shows 6 cores, but on task manager it shows 4 cores. I tried Cinebench R15 and the score is 600. Normally the I5 9400f shows scores 900. Intel...