Hi,
If the security only update installs first, the monthly rollup will still be applicable as it contains additional fixes (both non-security fixes and older security fixes) that are needed by the PC. The monthly rollup would then download and install,
providing the additional non-security fixes (and any security fixes from previous months).
For reference, the specific explanation in this article: "More on Windows 7
and Windows 8.1 servicing changes".
Hope the above can help you.
Regards,
Yic
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