The week number is correct as it is week 39. Check it in other apps or even a completely different account (Outlook at work for example). Week numbers have always been there and always been somewhat in the background. That's why they are usually a greyish colour (many apps do it this way). The only thing that gets highlighted is "today". In case of Pocket Informant (default theme) and the built-in calendar the colour used for the highlighting is red.