Cannot declare class x, because the name is already in use

i was trying to add a new column to my existing table admission_quota ,using the command :

php artisan make:migration add_application_portal_to_admission_quota_table --table=admission_quota

but, it returns an error:

PHP Fatal error: Cannot declare class AddReconcilateDateToTransactionTable, because the name is already in use.

what to do now ?