There are two procedures for resetting the TN-315, depending on whether you have a print-only device (HL series) or multifunction device (MFC series).
Multifunction Device (MFC series):

If you have a Brother multifunction (MFC series) machine and recently replaced your TN-315 toner cartridge, you can manually reset the toner remaining. This procedure has been verified for the Brother MFC-9460CDN & Brother MFC-9560CDW.
1. Open the front cover.
2. The display should read “Cover Open”.
3. Press the “Clear” button.
4. “Reset Menu” appears on the LCD display. Press the up or down arrow button to select the toner cartridge that needs to be reset.
5. After selecting the appropriate toner cartridge press OK.
6. Press “1”for reset and then the display will show accepted.
7. Press the Stop/Exit button.
8. Close the front cover and the operation has now been completed.
Print-only Device (HL series):

If you have a Brother print-only device (HL series) machine and recently replaced your TN-315 toner cartridge, you can manually reset the toner remaining. This procedure has been verified for the Brother HL-4150.
1. open toner cover
2. Press ‘secure’ and ‘cancel’ buttons simultaneously
3. scroll through color options menu
4. press ‘ok’ button when on desired color
5. Follow menu options for reset
6. close toner cover