Zend certified PHP/Magento developer

mailchimp Create Merge Fields in magento 1

When I click on button Create Merge Fields i got error in log file

2019-10-29T16:47:37+00:00 DEBUG (7): Merge Max Limit Exceeded for Api Call: [https://us15.api.mailchimp.com/3.0/lists/7e3c61605f/merge-fields/] using method [POST]
Detail: [You have exceeded the maximum number of 30 merge fields for this list.]
Params:
{“name”:”Middle Name/Initial”,”type”:”text”,”tag”:”MNAME”,”public”:true}

i use last mailchimp extension version.
My Customer Fields Mapping:
enter image description here

What is wrong in my config?