Level-Number
Level numbers 1 through 49 indicate the position of a data item or screen item within the hierarchical structure described by a screen description entry.
General format
General rules
1. The level-number 1 identifies the first entry in each screen description.
Syntax Rules
1. A level-number is required as the first element in each screen description entry.
2. A level-number in the range of 1 through 9 may be specified as 01 through 09.
3. Screen description entries shall have level-numbers 1 through 49.