Once you leave the first page (by pressing next) pressing the browser's back button causes you to remain on the webpage chosen by the numbered or next button until you've pressed the back button a sufficient number of times to leave the webpages entirely, then you return to where you came from without going back to each prior page. It is as though no updated history is stored.
Go to your Global Inbox.
Press next a few times.
Press your browser's back button.
Notice you would remain on page 4, never revisiting 3, 2 and 1; upon the fourth press you would return to where you came from (back works correctly, eventually).
You ought to be able to press any combination of next, numbered, and prev buttons and when you press your browser's back button you should go back one webpage. Pressing and holding the back button (to pop-up the history) shows all the back-links but choosing one doesn't take you back, instead you remain on the numbered page until 'you have exhausted your backs' then you jump away.
Note: There are other Bug Reports about the Browser back buttons not working in other situations but none regarding the Global Inbox. EG: The browser's "Back" button cause problems with the review buttons.