I was thinking there was a way to calculate it with a equation. I just made this to count the total number of records.

alias CountHash {
  var %TableCount = $hget(0), %TotalCount
  While %TableCount {
    %TotalCount = $calc(%TotalCount + $hget(%TableCount,0).item)
    dec %TableCount
  }
  return %TotalCount
}

I'm sure this would be useless in calculating anything, since the amount of memory is set at the end of the hmake statement. I'm guessing if you always use 10, it would be
(10 $hget(0)) (Whatever amount of memory = 1 in hmake)