Why is the committed memory reported by PSAPI smaller than the used physical memory?

Question

This question concerns the PERFORMANCE_INFORMATION struct from the Process Status API (PSAPI) on Windows.

From the documentation, I would assume that CommitTotal >= (PhysicalTotal - PhysicalAvailable) since CommitTotal also includes the page file in addition to physical memory.

However, on my system I get the following values that violate the assumption:

• CommitTotal = 7,943,270,400 (~ 7.4 GB)
• PhysicalTotal – PhysicalAvailable = 9,685,630,976 (~ 9 GB)