Any idea why?

PS C:\Windows\system32> $propFolder = (Get-ChildItem "C:\Proprietary" -recurse | Measure-Object -property length -sum)
PS C:\Windows\system32> $propFolderSize = "{0:N2}" -f ($propFolder.sum / 1MB)
PS C:\Windows\system32> $propFolderSize
85.20
PS C:\Windows\system32> $propFolderSize -gt "150"
True

Does anyone have an idea why it is evaluating to True? the $propFolderSize clearly shows its 85.20 and it is somehow showing me that it is greater than 150.