How can I increase the number of characters allowed to be entered in this field?

In our system, we have a tab where temporary alarm suppressions are listed and there is a column for 'suppression reason' where the supervisor should enter comments about the alarm and the suppression. However, each line only allows 40 characters to be entered in that cell, so there is not enough room to use this to the extent we would like. Does anyone know how to increase the amount of characters allowed here?