The System worksheet is one of the worksheets found in the Lertap5.xlsm workbook -- you can see its tab down towards the bottom of this screen snapshop:
The Comments worksheet is displayed above. To see the System worksheet, just click on its tab.
The System worksheet looked like this as of February, 2005:
If you're looking at this page using an interactive version of Lelp (not a printed PDF version), you should find that some of the rows above may be clicked on -- many of the rows hyperlink to corresponding Lelp topic pages.
If the row of interest to you does not hyperlink, you might try referring to the manual for a suitable discussion; as an example, Row 12, the percentage of N found in upper and lower groups, is not discussed in Lelp: see Chapter 10 of the manual (look at page 166 if you have the good fortune of having a printed copy of the manual).
We used to ship Lertap with the System worksheet hidden in order to discourage less experienced users from fooling around and getting into trouble. Trouble is especially likely to result if the settings in Rows 3, 4, and 5 are altered.
If one of the Present Settings is changed, sometimes the Lertap5.xlsm workbook has to be closed and then re-opened before the change will be effected. However, numerous settings take effect immediately, and do not require closing Lertap. Among these are the settings seen above in Rows 12 through 17, and in Rows 19 through 24 -- if you alter the column 2 setting in one of these rows, the change will take effect without having to close Lertap and then re-open it. (But don't read too much into this. If, for example, you change the item difficulty calculation method via row 19, the item difficulties you've already obtained will not change until you once again use the Run menu.)
Note 1 inserted May, 2005: a "production mode" capability was added to Lertap, with relevant options set in rows 26 through 29 of the System Worksheet. A simple click here will take to you the corresponding topic. (The row-position of these options changed after the following was inserted.)
Note 2 inserted July, 2005: support for response-similarity checking was added, with relevant options set in rows 25 through 27 of the System Worksheet. A simple click here will take to you the corresponding whatchamadoodle.