Image memory size restriction PL/SQL code oracle apex 5.1

1. Right Click on the File Browser item name and create a Validation Action 
2. Then write this code as PL/SQL function body return text as condition
(Please replace the name of File Browser item name like "P15_RCAPPIMG_temp")

 declare
 cursor c is 
 select doc_size
 from apex_application_files
 where name = :P15_RCAPPIMG_temp;
 v_size number := 0;
 v_msg varchar2(100);

 begin
 open c; 
 fetch c into v_size; 
 close c;
 --Here is 15360 means 15kb image size because 1 latter= 8 byte 
 if (v_size < 15360) then
 v_msg  := 'Image must be at least 15KB!';
 DELETE from APEX_APPLICATION_FILES WHERE name = :P15_RCAPPIMG_temp;
 return v_msg;

 elsif (v_size > 30720) then
 v_msg  := 'Image size cannot be more than 30kb!';
 DELETE from APEX_APPLICATION_FILES WHERE name = :P15_RCAPPIMG_temp;
 return v_msg;

 end if;
 end;