Column Width: Field is used for adjusting the width of the fileds in the list. Field Hiegh and Field Length entries are used for the field width and hieght in FORM view. Take can example to explain how to use "Column Field". Below figure is account's search result. If more columns are shown then some become very small making their headers invisible. See the highlighted headers.
In the filed "Column Width" you enter value (Say 20) which mean that field will occupy 20% of total LIST. All other column will adjust in the remaining 80% width. if the value is entered in lot of fields in LIST it will be relative to number entered in all other fields. I will make the "Title" field little bigger. Open the transacion CRMC_BSP_CT for new customizng tool. you use the old transaction (CRMC_BLUEPRINT_C) to navigate to the fieldgroup customizing. Open the application: CRMM_ACCOUNT Navigate to the reference field group "ACC_SRES_LOG_NAM_V1". as shown:
Enter the value 15 in the column width field. Enter the value 12 for the field "BP_Name2", Which will make that field little shorter.
Now you can see the LIST column are adjusted as per the above customization. Note: You can't use this customizing for reference field groups. You should put the value for individual fields in reference groups.