Entry page will not work in this scenario as entry page is a visit
scoped dimension, all time within a given visits would be attributed to
that entry page. You can however filter by hit depth = 1. If you need to
filter to the first page within the first visit you could use visit
depth = 1 and hit depth = 1. Please note that bounces are not included
in any time calculations (as there is nothing to subtract from)..