you will need to edit the code used to out put that column using the php substr() function.
the code to output the column will look like this:
<?php echo $row_recordsetName["ColumnName"]; ?>
using the substr() function, you can set it to show only the first 50 characters:
<?php echo substr($row_recordsetName["ColumnName"], 0, 50); ?>
see the following page for more details on the php substr() function:
function.substr.php