if you are using running totals and it is possible to make it work, DBlank will figure it out for you.
Depending on how the data is structured (which is DBlank question) I would use formulas with shared variables to do the counting. It is more complex than running totals (probably, I don't use running totals because they don't seems as straight forward to me as the formulas) but accomplish the same thing.
In general there is a reset formula, that will set your variables back to 0, this I place in the group header (proably the tool for you). There is a display formula that usually goes in the group footer, you would need 2, 1 for warranty, one for warranty and paid (if I understand correctly). Finally there is the 'tough' formula, the incrementer. It tends to look something like:
shared numbervar warranty;
shared numbervar paid;
if {table.warranty}=true then
warranty := warranty +1;
if {table.paid}=true then
paid := paid +1;
"" //to hide the calculations (looks silly with a number floating around.
This formula usually goes in the details section of the report.
Hope this helps. Again, if you need help with running totals DBlank is your man, he has helped plenty of others with running totals.