Line 14 *could* be assets put in service in those years, and expensed 100% in the year of acquisition.

Line 17 is problematic.  You should ask the prior preparer for the schedule (but if it's Laura, she won't give it to you). 

Is line 17 the same for 2020 & 2021?  If so, you could divide by 3.636% to get the (depreciable) basis of the rental, assuming it is residential rental property.  This would only work if the only asset is real property, and it won't give a land value.  

Does the client have any clue what s/he paid for the property and when it became a rental?

Also ask for prior years, as many as your client has to see if one of them has a depreciation schedule.

AND - discuss an extension as the deadline is close.