ReplacableToken_ when using web.config transform?

I have a web.config with 2 transforms - for debug and release.

web.config:

<connectionStrings>
    <clear />
    <add name="StrName" connectionString="data source=.\sqlexpress;User Id=sa;Password=pass;Database=SocialBot;"
                providerName="System.Data.SqlClient" />
</connectionStrings>

I just copied the example given and replaced the name with StrName. I end up with :

<add name="StrName" connectionString="$(ReplacableToken_SocialBotConnectionString-Web.config Connection String_0)"
                providerName="System.Data.SqlClient" />

What the hell is ReplacableToken_ ?

I have another project and it works with no problem there.