Please post a screenshot, and attach your data file and m-code to read it in and plot it, if you can.
Be aware that skewness is determined not only by how many data points are to the right and left of the mode but also how far away they are . So more points that are on the left but close to the mode, may not overwhelm a few points that are on the right but much farther away, giving an overall positive skewness even though more points are on the left. Here is the formula for an image:
skewness = sum((GLs - meanGL) .^ 3 .* pixelCounts) / ((numberOfPixels - 1) * stdDev^3);