How to align window to windows' taskbar - c++

Question

I'm trying to position my Win32 API window alongside (e.g. left-sided vertical) taskbar. My display has 2560x1600 resolution and 144 DPI. I had some problems with DPI-aware apps previously, so maybe I still don't undestand some DPI-related things. For example, now I set DPI-awarness both programmatically - setting the DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 option through the Win32 API, and adding two lines (to support Windows 7-10) to the project's manifest file:
<dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">True/PM</dpiAware>
<dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
Here is a code snippet, that shows how I'm setting a window's position:
RECT taskbarRect = {0, 0, 0, 0};
HWND taskbarHandle = FindWindow(L"Shell_TrayWnd", NULL);
if (taskbarHandle) {
GetWindowRect(taskbarHandle, &taskbarRect);
} else {...}
RECT notificationWindowRect; // Here is the RECT for window, I'm trying to reposition.
GetWindowRect(notificationWindowHandle, &notificationWindowRect);
LONG newX = 0;
LONG newY = 0;
bool taskbarIsVertical = (taskbarRect.Height() > taskbarRect.Width());
if (taskbarRect.left == 0 && taskbarIsVertical) { // left vertical taskbar
newX = taskbarRect.right;
newY = taskbarRect.bottom - notificationWindowRect.Height();
} else {...}
SetWindowPos(notificationWindowHandle, NULL, newX, newY, 0, 0, SWP_NOSIZE | SWP_NOZORDER | SWP_NOACTIVATE);
When system scaling is set to 100%, it's almost working - taskbarRect has a width of 63, but still there is a gap of a few pixels between the taskbar's right side and my window's left side. Note, that my window has the popup style and has no borders.
However, the main problem happens, when I set Windows' scaling to 150%. From the one hand, the taskbarRect's width becomes equal to 94, which I suppose is correct because 63 * 1.5 == 94. On the other hand, my window becomes hidden a little bit from the left side by the taskbar. To handle that, I need to add 65 pixels:
newX = taskbarRect.right + 65;
I don't understand where this 65-pixel shift appears from, and why it is exactly 65 pixels.