Sales Dashboard

Dear Sellers,

I have been looking at our sales over a period of 12 months from 1. november 2019 to 31. october 2020.

I struggle to understand something.

When i take the full period: 1. november 2019 to 31. oktober 2020 i get X-amount of ordered sales.

However when i break those months up for the period (so i get a sales ordered number for each month) and add each month up i get an amount that are are around 5-7 percent higher.

Can someone explain to me what the issue is?

Thank you very much in advance,