Nanao MS-2930 Geometry Help!!

[koki]

My Nanao MS-2930 monitor have “Barrel Distortion” issues as in following pictures;

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I think the one of these knob on chassis should fix this issue. But I want to know exactly which one control this since the far side knobs is very hard to reach
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Any help would be appreciated!

 

[nem]

S.P.C 15 is the one you want. Third one from the top.

 

[koki]

S.P.C 15 is the one you want. Third one from the top.

Thank you.