The SHRINK command removes a number of rows at the end of a table. \madbox SHRINK, TABLE=tabname, ROW=integer;

The SHRINK command takes two arguments:

TABLE is the name of the table from which rows should be removed. The table must have been previously created and filled or read from file with READTABLE or READMYTABLE.

ROW is the number of the last row to be kept in the table. All rows beyond the given row number are removed.
Negative values are allowed and count the row numbers from the last row, allowing access to the table in reverse order of rows: ROW = -1 removes the last row of the table, ROW = -2 removes the last two rows of the table, etc…
(Default: -1)

Trying to access the table forward beyond the last row, i.e. ROW strictly greater than nrow, where nrow is the number of rows in the table, or trying to access the table backwards before the first row, i.e. ROW strictly lower than -nrow, both result in a “row out of bound” message and no values are filled in the table.

Many commands in \madrequire the prior setting of various quantities related to the beam in the machine. Therefore, \madwill stop with a fatal error if an attempt is made to expand (USE) a sequence for which no BEAM command has been issued before.