Your formula (C38/COUNT(C6:C36))*31 takes the average daily sales and
multiplies by the number of days in the month, which is why it matches
the total sales amount.

If you have a date associated with each daily sales figure, you might
use the WEEKDAY function to sum sales for each Monday, each Tuesday,
etc. This would show how each day contributes to your total monthly
sales figure, and (from a marketing perspective) would provide
visibility as to what day you might have a sales promotion.

For instance: to get total sales for all Sundays:
=SUMPRODUCT(--(WEEKDAY(B6:B36)=1),C6:C36)
.... assuming your dates are in B6:B36.

Note the sum of these numbers will still add up to your total sales
figure; from here you can apply historical percentages of sales
increase / decrease (if you have that data) to make projections.