The % of Total is the standard deviation for each source of variation, divided by the total standard deviation and multiplied by 100.
The percentage of the total standard deviation is the square root of the variance for each source. Thus, the variance percentages sum to 100, but the standard deviation percentages do not.
Use the percentage of the total standard deviation to compare the variation from each source to the total variation.
If a variance component estimate is less than zero, Minitab displays the negative estimate, but sets the estimate to zero in order to calculate the percent of total variability.