The total amount is greater than 0. In testing I've duplicated the issue but taking the following steps:
1) Create a PO with 2 lines:
First line is for an item with qty = 2
Second line is for the same item with qty = -1
2) Receive (post) the following -- this works
First line, receive 1
Second line, receive -.5
3) Receive a second time (post) the following -- receive the above error
First line, receive 1
Second line, receive -.5 or anything
Here is the actual error:
Item Shpt. Entry No. must be equal to '0' in Item Journal Line: Journal Template Name=, Journal Batch Name=, Line No.=0. Current value is '6679'.