...
The dialog offers a few examples in the drop-down
User can specify their own pattern by typing in their specification, such as:
With the following XY2Z designation, the imported columns will be XYZZXYZZ......
XYZ First two cols will be set as X, Y, the rest will be set as Z
(XYZ) Use the pattern XYZXYZXYZ...
X(YZ) Use the pattern XYZYZYZ....
X(Y2Z) Use the pattern XYZZYZZYZZ
X2(YZ) Use the pattern XYZYZZZ...