Sum exclude duplicates if below each other

In the formula

=SUM(IF(A2:A11="",A1:A10))

you have to pay attention to the cell references in red.
Where A1= the cell just above your first number and A11=the cell below the last sum of a group, assuming your numbers are in the range A2:A10.

Change it as per your need and if this doesn't work, it would be better if you upload a sample workbook.
See the attached sheet where the formula is applied for the example data in post#1.