Q: What does the status "Decision in progress" mean?

You have not mentioned whether there were any other statuses before "Under review," so it's difficult to say if this is the internal editorial check or the external peer review. If the status changed to "Under review" directly after submission without any interim changes, it is likely to be the initial editorial screening. If that is the case, the status "Decision in progress" might be indicative of a rejection. However, if the "Under review" referred to the external peer review, you can be hopeful. Whatever it is, you should be informed of the decision soon. 

All the best!

Related reading:

• Does a direct 'Decision in Process' status indicate rejection?
• Can the status change to "Decision in process" without a request for revisions?
• Why did my manuscript's status change from "With Editor" to "Decision in Process"?