Good afternoon,
Xray shows minimal changes in the 2nd molar and might need a filling. Can be confirmed after seeing clinically.
Pocket is related to gums and can't be seen on xrays (only bone and teeth are seen on xrays), but you may see slight bone loss. Deep scaling as suggested by the doctor will take care of the of 4mm pocket. 4mm pocket means it's in the initial stage and nothing to worry. It needs some attention and you will be fine after treatment.
Next Steps
go to the dentist and get it done as suggested by him.
Health Tips
Deep cleaning is not a harmful procedure, so don't worry.
If required, do contact me