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The keystone correction standard for the Cosmos 4K SE when projecting from the side is: at a projection distance of 2 meters, the height difference of the edges on both sides should be less than 2%. 

Insider information:

Projection distance is 2 meters:

20 degrees: height difference <15mm, 30 degrees: height difference <20mm.

Projection distance is 3 meters:

20 degrees: height difference <25mm, 30 degrees: height difference <30mm.

We apologize for any inconvenience this may cause.

If the above solutions cannot solve your issue, please contact Nebula Customer Support at support@seenebula.com for further assistance.