That means it first considers the blog title which you had written as shown in the image below and then the post title.
Here is what you have to doBefore you change anything taking a backup of the template is recommended. Go to Template. Click on Edit html. Click Proceed. Find the code below
<b:if cond='data:blog.pageType == "index"'> <title><data:blog.title/></title> <b:else/> <title><data:blog.pageName/></title> </b:if>
Preview the template to see whether it gives any error and then save. You are now done. Now search engines will consider your post titles as the title tag of the post concerned.
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