Epson PowerLite L520W Operation Manual page 49

Note: You can also open the Effect settings screen from
Duration (secs.)
Apply
Selects the time that each file is displayed before switching to the
next file automatically. You can enter 1 to 60.
(Only displayed when the Effect settings screen is opened in the
Preview screen)
Applies the value set in Duration (secs.) to the Preview screen.
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in the Detail area of the project screen.