Multiple ASPSESSIONID in cookies Not Resolved - asp.net

Question

I have problems like in this example
I also create that script:
<% If trim(Session("test_val")) = "" Then
Dim my_num
Randomize
number = Int((rnd*1000))+1
Session("test_val") = number
End If
%>
<b>Session ID:</b>
<% response.write(Session.SessionId) %><br /><br />
<b>Session("test_val"):</b>
<% response.write(Session("test_val")) %><br /><br />
<b>Session Timeout:</b>
<% response.write(Session.Timeout) %> minutes<br /><br />
<b>Server Software:</b>
<% response.write(Request.ServerVariables("SERVER_SOFTWARE")) %><br /> <br />
<b>HTTP_COOKIE:</b> <% response.write(Request.ServerVariables("HTTP_COOKIE")) %>
After each page request I got a different result
Session ID: 619163854
Session("test_val"): 784
Session Timeout: 480 minutes
Server Software: Microsoft-IIS/8.5
HTTP_COOKIE: ASPSESSIONIDQQATDABC=EMAJHOECJIKDFKKHFFKIGDEK
and
Session ID: 619245915
Session("test_val"): 39
Session Timeout: 20 minutes
Server Software: Microsoft-IIS/8.5
HTTP_COOKIE: ASPSESSIONIDQQATDABC=EMAJHOECJIKDFKKHFFKIGDEK; ASPSESSIONIDQSDTCDCB=OMALHOECNLEJLAHGOJEGDNIJ; ASPSESSIONIDQSATDBAD=EFBPIOECEIAAAGKFOJMECCOM; ASPSESSIONIDQQCTCAAC=LFBPIOECGGPIJAINBPKIDNFF
And every refresh ASPSESSIONID still appending to cookies
web.config
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rewriteMaps>
<clear />
<rewriteMap name="Static URL Rewrites">
<add key="/robots.txt" value="/robots.asp" />
<add key="/sitemap.xml" value="/sitemap.asp?format=XML" />
<add key="/sitemap.txt" value="/sitemap.asp?format=TXT" />
</rewriteMap>
<rewriteMap name="Static URL Failures">
<add key="/robots.asp" value="/" />
<add key="/sitemap.asp" value="/" />
</rewriteMap>
</rewriteMaps>
<rules>
<clear />
<rule name="Static URL Rewrites" patternSyntax="ECMAScript" stopProcessing="true">
<match url=".*" ignoreCase="true" negate="false" />
<conditions>
<add input="{Static URL Rewrites:{REQUEST_URI}}" pattern="(.+)" />
</conditions>
<action type="Rewrite" url="{C:1}" appendQueryString="false" redirectType="Temporary" />
</rule>
<rule name="Static URL Failures" patternSyntax="ECMAScript" stopProcessing="true">
<match url=".*" ignoreCase="true" negate="false" />
<conditions>
<add input="{Static URL Failures:{REQUEST_URI}}" pattern="(.+)" />
</conditions>
<action type="CustomResponse" statusCode="404" subStatusCode="0" />
</rule>
<rule name="Prevent rewriting for static files" patternSyntax="Wildcard" stopProcessing="true">
<match url="*" />
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile" />
</conditions>
<action type="None" />
</rule>
</rules>
</rewrite>
<defaultDocument>
<files>
<remove value="default.aspx" />
<remove value="iisstart.htm" />
<remove value="index.html" />
<remove value="index.htm" />
<remove value="Default.asp" />
<remove value="Default.htm" />
<add value="index.asp" />
</files>
</defaultDocument>
<directoryBrowse enabled="false" />
<httpErrors errorMode="DetailedLocalOnly" defaultPath="D:\err.html">
<remove statusCode="401" subStatusCode="-1" />
<remove statusCode="403" subStatusCode="-1" />
<remove statusCode="404" subStatusCode="-1" />
<remove statusCode="405" subStatusCode="-1" />
<remove statusCode="406" subStatusCode="-1" />
<remove statusCode="412" subStatusCode="-1" />
<remove statusCode="500" subStatusCode="-1" />
<remove statusCode="501" subStatusCode="-1" />
<remove statusCode="502" subStatusCode="-1" />
</httpErrors>
<urlCompression doStaticCompression="false" doDynamicCompression="false" />
<httpProtocol>
<customHeaders>
<remove name="X-Powered-By" />
</customHeaders>
</httpProtocol>
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="4290000000" />
</requestFiltering>
</security>
</system.webServer>
<system.web>
<sessionState mode="Off" />
</system.web>
</configuration>
I have 1 app pool
why:
Session Timeouts is changed?
ASPSESSIONID multiplying?

Answer 1

https://msdn.microsoft.com/en-us/library/h6bb9cz9(v=vs.71).aspx
Please change your
<system.web>
<sessionState mode="Off" />
</system.web>
or delete this section