DSPF Preview displays fields/constants with "+n" position notation incorrectly

**Describe the bug**
The DSPF Preview displays fields/constants with "+n" position notation incorrectly.

**To Reproduce**
Steps to reproduce the behavior:
1. Open a DSPF source with fields/constants that use "+n" position notation
2. Click on 'Preview '

**Expected behavior**
The "+n" position notation is standard syntax in DDS DSPF and PRTF sources. The preview should recognize this correctly and "remember" the correct line in which the field/constant should be displayed.

Example:
```
A FIELD1 10A 2 11
A FIELD2 10A +1
```

- FIELD1 appears correctly in line 2 position 11.
- FIELD2 should appear also in line 2 position 22.

**Screenshots**

**Environment (please complete the following information):**
- Extension version 0.1.2
- IBM Bob version 2.0.1
- VSCode version 1.121.0
- IBM i OS version 7.5 TR7

Reproduce the issue in the VS Code extension by opening a DSPF source with the provided FIELD1/FIELD2 example and selecting Preview . Trace how the preview handles "+n" positions; it is done when FIELD2 is rendered on line 2 at position 22 while FIELD1 remains at position 11.

Written by the indexing model from the issue text.