You need to increase the excerpt length. (An excerpt is what the slider displays.)
This has been discussed many times in this forum. A quick search should turn up the information you require.
Feel free to search both this forum and the Graphene documentation (http://docs.graphene-theme.com/) if we don’t come to your aid immediately. Everybody here has a full time job (or more) outside this free support forum. If you can’t find it here, you can often Google your issue (this is especially true in the case of error messages); just be sure to append “WordPress” to your search query. If it’s really urgent, you can always hire someone at jobs.wordpress.net, although that is a community of freelancers, and so you will definitely want references before hiring someone.
This free Support Forum relies on contributions from our support staffs and fellow Graphene themes users. While we endeavour to provide adequate and timely support, due to its voluntary nature responses are not guaranteed and may be delayed.
If you require urgent assistance, you may like to consider our Priority Support option.