Indexes is the number of elements in the delta table, in this case 8, you can count them.

NumbDeltas is the total number of vertices of this body part.

In theory there should be 26 deltas in the table (the same number as the vertices number), but as 18 morphed vertices have the value d 0 0 0 it are supressed remaining 8 deltas that are not d 0 0 0. This is done to reduce the table length removing useless information.

The value of indexes must match the number of delta entries. If you change to 9 in your case, Poser will read { as a number and { is not a number and who knows what Poser will do.

If you change indexes to 7 Poser will read d 25 0 0 -0.05835599 when was expecting to read { and again, who knows what Poser will do.

Stupidity also evolves!