This is not answering your question directly, but the following is how I and others include AHV and other payments expected in the (far-off) future. (and thus may be an alternative option for you).
We don’t somehow calculate a fictitious amount to safely withdraw from later.
Make a table with one year per line.
All income and expenses annually gives wealth development.
Add the estimated AHV to your income at 65.
Such a predictive table is quite straightforward (esp. mathematically) to set up - see, for example, this example:
The table I set up for myself (before I saw Phil’s) looks remarkably similar.