@Ja_Kar_Breau You are correct about Connections benefit mechanics, but that isn’t really the main issue with the graph.
The standings transactions below the graph are recorded as a percentage reward on a fixed 10.0 point scale, not an absolute value relative to your standing and accounting for the standings gain formulas as many believe them to be. The math used to generate the graph takes your correct current standings value at the right, then subtracts a percentage value from a decimal value to derive all of the other data points (core of the bug).
You can demonstrate this for yourself easily by running a mission with a known fixed reward like the SOE epic arc (7% base bonus / 8.75% with Social V). You will have an entry for 0.7 (0.875 with Social V) which is clearly just subtracted from your new standings to create the previous point on the graph, even though this is not what you gained. Similarly, running the same mission for the same corp always produces the same (percentage) value in the log, not an adjusted gain/loss using the standings formula.
I think the only time Connections comes in is that when you train Connections or lose levels due to lapsing Omega, this won’t be reflected in the previous graph entries since your historical standings and Connections levels are not stored server side at all, only your current/adjusted standing and the history of transactions.
I have an accepted bug report on this from a long while back. I don’t think it is a priority for CCP since most players don’t even notice the issue and current standings are correct.
As to OP, it’s a combination of the bug (graph is wrong) and the usual standings mechanics others have pointed out (the loss was scaled against 19.6, the distance to -10.0, and gains were scaled against 0.73 / 0.7 / 0.68 / 0.67, the respective distances to +10.0).