This error occurs when a duplicate labels are present in a function. %s : duplicated label
Use labels with a margin of 5 points, like 000, 005, 010, so that any intermediate labels when introduced can have a label with number in between.
Example
[#Menu: Gateway of Tally]
Add: Item: "MyReport": Call: MyFunc
[Function: MyFunc]
000: Display: DayBook
000: Display: Trial Balance
In the above example, the label 000 is specified twice in the function MyFunc . Hence the message error T0030: Duplicate label 000 in procedural block.
The code is corrected by renaming the second label to 005.
[#Menu: Gateway of Tally]
Add: Item: "MyReport": Call: MyFunc
[Function: MyFunc]
000: Display: DayBook
005: Display: Trial Balance