Zend certified PHP/Magento developer

Why is my Windows laptop reseeting file permission when I write to a file on a drive mapped to my macbook across same LAN?

When my Windows laptop writes to a file in a drive mapped to my macbook, on the same LAN, it changes the permission of the file
from “-rwxrwxrwx” to “-rw——-” which means I must go to the macbook to change the permission back to “-rwxrwxrwx” before my macos app (Xcode) can access the file.