Interpreting generations on Gedmatch

[LizzieL]

I have used Gedmatch free tool "People who match both kits" to match my kit and that of a 3C1R (J)
Results abridged
              match with me                    match with J
EB          55.7cM     4.0 gen      82.2cM       3.7 gen           0.3 gen diff
MK          37.0cM     4.3   gen          779.6cM       2.1 gen    2.2 gen diff
GB          15.7cM     4.9   gen           15.6cM       4.9 gen     0.0 gen diff

If I compare my results with MK
               match with me                    match with MK
J              67.6cM     3.9 gen           779.6cM        2.1 gen   1.8 gen diff

MK is also my half 3 C once removed. Her father and J's father were brothers. Their great great grandmother was my great grandmother's half sister. So our common ancestor is 4 generations back for me and five for them. Only one generation difference. Comparing MK with J, their common ancestors are grandparents so that would be two generations, which seems to fit with what Gedmatch says. But I don't see what the generations difference means apart from being a simple subtraction. How can I use the number of generations to find how EB and GB fit into my tree? The B in EB  and GB is different surname.

[Biggles50]

No easy way, unless you and them (or at lease one) are on Ancestry and they show up on Thrulines/ Common Ancestors.  The alternative is the possible long slog of building a tree, the first will be the hardest, then hopefully the rest will slot in far easier.

In Gedmatch to the right in the One To Many report will be the DNA testing company each used so looking there may result in them having an online tree which would help as long as it is accurate.

You are talking Great Great Grandparent level, baring any Pedigree Collapse, so 16 people or 32 if you want to go back a extra generation if and when you build a tree.

I have a tree if 700 around a highish match and there are 12/15 other DNA match’s now in the tree, it has taken a lot of time and effort to get there.

[LizzieL]

All of us are on Ancestry. J has a huge mistake in her tree. She gets back correctly to my great grandmother's half sister, but then has entirely the wrong parents for her, so no Thrulines match
MK has a  tree which correctly identifies the same ancestress and has the right parents, but only gives forename for the mother and no places or dates for either parent, so Ancestry doesn't connect her tree to mine. (MK passed away in 2019, her account is now managed by her sister). I had been in contact with both these ladies a few years ago, so I'm sure of the relationships.
EB has a small tree, she has identified all great grandparents, but not all lines are extended from there.
GB has an extensive tree for her maternal side, and for her paternal grandmother. Her paternal grandfather is unknown. All from USA.

[Biggles50]

Build a tree around EB using what you believe to be the right people and including their shared match’s with you.

Then upload the Gedcom into DNA Painters WATO tool, add the cM values and answer the questions.  WATO will analyse and report on the various hypothesis and score each.

It will respond by saying …. You are the x times grandchild of the person y in the tree

If it is wrong try a different set of questions and base person.

Read up on using WATO and the above will then make sense

Good luck