clarify AV1E_SET_TARGET_SEQ_LEVEL_IDX docs

this is a follow up to:
905abbb42 av1/arg_defs: use a valid target level index in help msg

the examples are updated to match and the provision to 'pad with leading
zeroes' is removed as it's somewhat misleading and padding the OP index
will make value octal.

Bug: aomedia:3184
Change-Id: I25bf73eda541dde0ca6e98622a9aea9b0a106f26
(cherry picked from commit 6d89b79a47572f516fd315602cfd96dd377cbaae)

aom/aomcx.h

diff --git a/aom/aomcx.h b/aom/aomcx.h
index be9007f..0dd200d 100644
--- a/aom/aomcx.h
+++ b/aom/aomcx.h
@@ -612,18 +612,18 @@
   AV1E_SET_RENDER_SIZE = 53,
 
   /*!\brief Control to set target sequence level index for a certain operating
-   * point(OP), int parameter
-   * Possible values are in the form of "ABxy"(pad leading zeros if less than
-   * 4 digits).
+   * point (OP), int parameter
+   * Possible values are in the form of "ABxy".
    *  - AB: OP index.
-   *  - xy: Target level index for the OP. Can be values 0~23(corresponding to
-   *    level 2.0 ~ 7.3) or 24(keep level stats only for level monitoring) or
-   *    31(maximum level parameter, no level-based constraints).
+   *  - xy: Target level index for the OP. Can be values 0~23 (corresponding to
+   *    level 2.0 ~ 7.3, note levels 2.2, 2.3, 3.2, 3.3, 4.2, 4.3, 7.0, 7.1, 7.2
+   *    & 7.3 are undefined) or 24 (keep level stats only for level monitoring)
+   *    or 31 (maximum level parameter, no level-based constraints).
    *
    * E.g.:
-   * - "0" means target level index 0 for the 0th OP;
-   * - "111" means target level index 11 for the 1st OP;
-   * - "1021" means target level index 21 for the 10th OP.
+   * - "0" means target level index 0 (2.0) for the 0th OP;
+   * - "109" means target level index 9 (4.1) for the 1st OP;
+   * - "1019" means target level index 19 (6.3) for the 10th OP.
    *
    * If the target level is not specified for an OP, the maximum level parameter
    * of 31 is used as default.

av1/arg_defs.c

diff --git a/av1/arg_defs.c b/av1/arg_defs.c
index a6b5aab..eb6346a 100644
--- a/av1/arg_defs.c
+++ b/av1/arg_defs.c
@@ -566,15 +566,14 @@
       ARG_DEF(NULL, "reduced-reference-set", 1,
               "Use reduced set of single and compound references (0: off "
               "(default), 1: on)"),
-  .target_seq_level_idx = ARG_DEF(
-      NULL, "target-seq-level-idx", 1,
-      "Target sequence level index. "
-      "Possible values are in the form of \"ABxy\"(pad leading zeros if "
-      "less than 4 digits). "
-      "AB: Operating point(OP) index, "
-      "xy: Target level index for the OP. "
-      "E.g. \"0\" means target level index 0 for the 0th OP, "
-      "\"1019\" means target level index 19 (6.3) for the 10th OP."),
+  .target_seq_level_idx =
+      ARG_DEF(NULL, "target-seq-level-idx", 1,
+              "Target sequence level index. "
+              "Possible values are in the form of \"ABxy\""
+              "AB: Operating point (OP) index, "
+              "xy: Target level index for the OP. "
+              "E.g. \"0\" means target level index 0 (2.0) for the 0th OP, "
+              "\"1019\" means target level index 19 (6.3) for the 10th OP."),
   .set_min_cr = ARG_DEF(
       NULL, "min-cr", 1,
       "Set minimum compression ratio. Take integer values. Default is 0. "