1. What type (model) of object is "o"? Do you have loop on "objects" - something like:
for each="o in objects"
otherwise ...if you use "o" directly, still "printing" list of multiple objects, "o" will point to first object in a list.
2. What variable is not what you expect? (l.debit, l.credit or o.partner_id.debit-o.partner_id.credit)
Kaspars
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