Hi,

suite.rc/flow.cylc as per below.

```
#!jinja2
[cylc]
UTC mode = True
[[parameters]]
x = 1..3
[scheduling]
initial cycle point = 20200101T0000Z
final cycle point = 20200101T1200Z
[[dependencies]]
[[[R1]]]
graph = ic => a<x>
[[[T00,T06,T12,T18]]]
graph = """
a<x+1>
=> b<x>
=> c<x>
"""
[runtime]
[[root]]
script = false
```

They produce different graphs for Cylc7 and Cylc8. Different results are expected for `x-1`

(thanks @oliver.sanders for pointing that out to me), but that documentation does not say that `x+1`

would produce different results. Based on the reasoning in the documentation, I imagine the `x+1`

case is expected too, but it is not documented.

For comparison, here are the reference outputs for both (just the edge part of the reference outputs)

### Cylc 7

```
$ cylc graph -r $PWD 20200101T0000Z 20200101T0000Z | grep edge
edge "a_x2.20200101T0000Z" "b_x1.20200101T0000Z"
edge "a_x3.20200101T0000Z" "b_x2.20200101T0000Z"
edge "b_x1.20200101T0000Z" "c_x1.20200101T0000Z"
edge "b_x2.20200101T0000Z" "c_x2.20200101T0000Z"
edge "b_x3.20200101T0000Z" "c_x3.20200101T0000Z"
edge "ic.20200101T0000Z" "a_x1.20200101T0000Z"
edge "ic.20200101T0000Z" "a_x2.20200101T0000Z"
edge "ic.20200101T0000Z" "a_x3.20200101T0000Z"
```

### Cylc 8

```
$ cylc graph -r $PWD 20200101T0000Z 20200101T0000Z 2>/dev/null | grep edge
edge "20200101T0000Z/a_x2" "20200101T0000Z/b_x1"
edge "20200101T0000Z/a_x3" "20200101T0000Z/b_x2"
edge "20200101T0000Z/b_x1" "20200101T0000Z/c_x1"
edge "20200101T0000Z/b_x2" "20200101T0000Z/c_x2"
edge "20200101T0000Z/ic" "20200101T0000Z/a_x1"
edge "20200101T0000Z/ic" "20200101T0000Z/a_x2"
edge "20200101T0000Z/ic" "20200101T0000Z/a_x3"
```

### What is different?

Cylc7 has `b_x3`

and `c_x3`

. Cylc8 does not. Either this is a bug or a gap in documentation for the Cylc7-to-8 changes. My guess is its the latter.