Ignore the 4th reel…
The first 3 reels are discoball, discoball and x6 so the win is £6.
The 4th reel multiplied the win x6 and so paid £36.
If the 5th reel dropped a x6 then it would be £36 x 6 so £216
If the 5th reel had a discoball then it would have paid 5 disco balls x 36
The x6 reels don’t extend the win, they just multiply the win unless the paying symbol follows them