siteid POSITION (*) SMALLINT siteloc POSITION (*) INTEGER
If these were the first two column specifications, then siteid would begin in column 1, and siteloc would begin in the column immediately following.
ename POSITION (1:20) CHAR empno POSITION (22-26) INTEGER EXTERNAL allow POSITION (*+2) INTEGER EXTERNAL TERMINATED BY "/"
Column ename is character data in positions 1 through 20, followed by column empno, which is presumably numeric data in columns 22 through 26. Column allow is offset from the next position (27) after the end of empno by +2, so it starts in column 29 and continues until a slash is encountered.