I already sketched the slope of lab result to find a value. But I need to do it in Excel which I will include in the lab report. But the slope value is different.

The one I got from sketching in the lab is y = 3333.333x which lead to a 12% error.

But when I use Excel trendline with intercept 0,0, the value is very different as shown in the picture. It's y = 0.696x which seems wrong.

The value that I put is the same as the paper: