Why are htop and system monitor showing different memory usages

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19

You look at the Memory Info in KDE.

Screenshot_20211201_153209
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It shows 3 different usages of the memory (buffers + cache + shared). You should calculate all 3 together.

You can compare it with htop, /free --mebi and system-monitor .

I checked them, but htop and system-monitor are not correct for me.

Edit:
Maybe system-monitor calculates all usages of memories from CPU and GPU?

htop, /free --mebi and system-monitor ignore the disk cache, so it is not calculated.