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Instructions:
Tools > Options > OO Draw > General > Unit of measurement: mm
Select the blue box and the thick black line together.
Note: Position (x,y)=(10,20)
See status bar.
Copy, paste
Pasted objects position is now offset and off-grid at 10,19.51
Same steps for each line at right, or both lines together:
Pasted lines are offset -1.24 mm
x,y = 10,20