[label="4X4FKWN2Q7YBS [1;1["]; – is it a sequence or encode number?

digraph {
node_AAAAAAAAAAAAA_0_0[label="AAAAAAAAAAAAA [0;0["];
node_AAAAAAAAAAAAA_0_0 -> node_4X4FKWN2Q7YBS_18_49 [label="[4X4FKWN2Q7YBS]", color="royalblue"];
node_4X4FKWN2Q7YBS_1_1[label="4X4FKWN2Q7YBS [1;1["];
node_4X4FKWN2Q7YBS_1_1 -> node_4X4FKWN2Q7YBS_2_17 [label="[4X4FKWN2Q7YBS]", color="forestgreen"];
node_4X4FKWN2Q7YBS_1_1 -> node_4X4FKWN2Q7YBS_18_49 [label="[4X4FKWN2Q7YBS]", color="orange"];
node_4X4FKWN2Q7YBS_2_17[label="4X4FKWN2Q7YBS [2;17["];
node_4X4FKWN2Q7YBS_2_17 -> node_4X4FKWN2Q7YBS_1_1 [label="[4X4FKWN2Q7YBS]", color="red"];
node_4X4FKWN2Q7YBS_18_49[label="4X4FKWN2Q7YBS [18;49["];
node_4X4FKWN2Q7YBS_18_49 -> node_4X4FKWN2Q7YBS_1_1 [label="[4X4FKWN2Q7YBS]", color="royalblue"];
node_4X4FKWN2Q7YBS_18_49 -> node_AAAAAAAAAAAAA_0_0 [label="[4X4FKWN2Q7YBS]", color="orange"];
}
()

This denotes a right-open interval, with [a,b[ = [1,10[ meaning an interval from 1 to 9 inclusive. It is from mod.rs:debug_vertex. The interval describes, bytes in a change (a file, maybe?), as far as I can tell.

It is indeed an open interval, meant to allow all the people who look at huge instances of these graphs to read them faster ;-)