64 on 80 is what on 100?

80. Simple scale. Not a grade table.

Does board actually scale like this?

For converting a paper to percent, yes. For CGPA tables, no. Different tools.

Change the new total box to 50. Works any two scales.

Percentage

Marks out of 80, show out of 100.

Obtained, original total, new total. Scaled = obtained / original × new.

Formula used: scaled = obtained / fromTotal × toTotal

This is an estimate. Your board formula may differ.

64 on 80 is what on 100?: 80. Simple scale. Not a grade table.
Does board actually scale like this?: For converting a paper to percent, yes. For CGPA tables, no. Different tools.
Out of 70 to 50?: Change the new total box to 50. Works any two scales.