Issue with Reconciliation when Averaging Weekly Variances and YTD Variances

Hello,

I have created a table to report the number of Changeovers by type (A-F) using a drop-down cell with a Week Number value. This table finds the variance between the weekly average Changeover time and a standard, and reports this variance by type in two forms: weekly and YTD. The ultimate goal of this table is to average all of the individual YTD variances to calculate one YTD average for one variance that incorporates all types of Changeover.

However, there is a discrepancy between the reported YTD Variance value and the value I get when averaging all of the Weekly variances. This is leading me to believe that one of my calculations is not correct. I am trying to determine the reason that my year-to-date (YTD) average and sum of weekly averages are not reaching the same value. Could this have anything to do with the conversions I am performing between numerical units (decimals) and time (in min)?

I can't seem to find why this is occurring and would appreciate any guidance.