The text of this message is: “For whom page will be checked out”.
But the word “checkin” in the tile suggests that the text should be: “For whom page will be checked in”.
This is corroborated by the overall context of the message and by the fact that the message with the same title with “-checkin-” replaced by “-checkout-” is identical to this one. Looks like they shouldn't be identical.
In addition, both of these messages would read better with a definite article: “For whom the page will be checked in/out”.
(These messages are related to the PageCheckout extension. I'm sorry, I could not find an appropriate label, so someone else will have to label this issue.)