The agreement between the Delta MEC and Delta. It grants preferential interviews to DCI pilots. This is Section 2.A. 176.f of your contract:

The Company will offer preferential interviews for employment to airmen employed by a Delta Connection Carrier that offers preferential hiring to such furloughed pilots, subject to the Company’s objectives for diversity and experience among newly hired pilots, and subject to the Company’s hiring obligations under the NWA CBA LOAs as they appear in LOA #9 (i.e., NWA LOA 2006-10, 2006-14, and 2008-01). A pilot hired by a Delta Connection Carrier operating any of the 70- or 76-seat jets not being operated as of November 1, 2004 will not be required to resign his Delta seniority number in order to be hired by such carrier. Preferential hiring rights at Delta Connection Carriers for pilots furloughed by the Company provided herein will be in addition to any flow down rights such furloughed pilots may have pursuant to the NWA CBA LOAs as they appear in LOA #9 (i.e., NWA LOA 2006-10, 2006-14, and 2008-01). These provisions will apply to carriers that operate 70- or 76-seat jets for the Company as a result of a merger transaction no later than one year after the closing date.

g. The Company will offer preferential interviews for employment to airmen employed by carriers (whose airmen were represented by the Association) at the time those carriers ceased operations, subject to the Company’s objectives for diversity and experience among newly hired pilots and subject to Section 1 B. 40. f.

The Flow Through LOA's (adopted by DAL via LOA #9) then clarify the flow arrangements. They are 2006-14 76-Seat Small Regional Jet Flow-through Agreement and 2008-01 Mesaba Flow. Since I only have them in pdf, I'll paraphrase: Pilots hired outside the Flow will not count against the totals within the Flow. The term is "...in addition to..."