For ODTAB flows to work correctly, you must specify turning movements on each lane, via the Nearside Movement etc data item fields for each lane. This is so that the ODTAB flows can be allocated across traffic streams according to the left/straight/right movements on the lanes in the traffic streams.
For the turning proportions to be correctly calculated, you must set up the arms to follow the naming convention used in OSCADY Classic, that is, each numbered arm must be positioned clockwise from the previous arm for drive-on-the-left or counter-clockwise for drive-on-the-right. Otherwise, the turning proportions grid will be inconsistent with the ODTAB grid.
Furthermore, ODTAB can only be used when there are either three or four arms in the junction. If your junction has more than four arms and you need to use ODTAB, you could consider merging two close together arms into a single OSCADY PRO arm. (You can then use the Keep traffic streams on each arm together option in the Junction Diagram screen to allow the individual traffic streams to be moved separately.)
The arm numbering convention for ODTAB is shown below, where A = Arm 1 etc.
In more complex cases, it may be better to use the DIRECT data option and input individual flows for each traffic stream.