Those are symbols from (most likely) Windows-1252 encoding of memory bytes. On the left side you can see actual values of memory. And on right you can see same values as "symbols". Here is table that is used to get those "symbols" from byte values:
https://en.wikipedia.org/wiki/Windows-1252#Code_page_layout
So for example value "32" will give you space symbol " ". Value "72: is "H" symbol. And so on...
If you would write this in C code:
And inspect what value does ch variable contain in debugger, you would see "H" symbol.
All unprintable symbols (like with value 0 or 1 and similar) are displayed as "." symbol.