diff --git a/specification/grammars/annotation.lark b/specification/grammars/annotation.lark
index b67e520..baee0fa 100644
--- a/specification/grammars/annotation.lark
+++ b/specification/grammars/annotation.lark
@@ -78,10 +78,10 @@ series_named_compound : "_" "{" CHARACTER+ "}"
 
 series_smiles : "s" "{" SMILES+ "}"
 
-series_unknown : "?" NUMBER*
+series_unknown : "?" ORDINAL?
 
 ion_series : series_peptide | series_immonium | series_internal | series_reporter | series_formula | series_named_compound | series_smiles | series_unknown
 
 analyte_reference_ion_series : (analyte_reference_ ion_series) | ion_series
 
-annotation : is_auxiliary? analyte_reference_? ion_series neutral_loss* isotope? adducts? charge? annotation_qualifiers?
\ No newline at end of file
+annotation : is_auxiliary? analyte_reference_? ion_series neutral_loss* isotope? adducts? charge? annotation_qualifiers?
diff --git a/specification/reference_data/reference_molecules.md b/specification/reference_data/reference_molecules.md
index 3d3b09d..deb9d3e 100644
--- a/specification/reference_data/reference_molecules.md
+++ b/specification/reference_data/reference_molecules.md
@@ -1,4 +1,4 @@
-|             | label_type   | molecule_type    | chemical_formula      |   ion_mz |   neutral_mass |
+|     name    | label_type   | molecule_type    | chemical_formula      |   ion_mz |   neutral_mass |
 |:------------|:-------------|:-----------------|:----------------------|---------:|---------------:|
 | TMT126      | TMT          | reporter         | C8N1H15               |  126.128 |                |
 | TMT127N     | TMT          | reporter         | C8[15N1]H15           |  127.125 |                |
@@ -43,4 +43,4 @@
 | TMT130N-ETD | TMT          | reporter         | C4[13C3][15N1]H15     |  117.131 |                |
 | TMT130C-ETD | TMT          | reporter         | C3[13C4]N1H15         |  118.141 |                |
 | TMT131N-ETD | TMT          | reporter         | C3[13C4][15N1]H15     |  119.138 |                |
-| TMT131C-ETD | TMT          | reporter         | C2[13C5]N1H15         |  118.141 |                |
\ No newline at end of file
+| TMT131C-ETD | TMT          | reporter         | C2[13C5]N1H15         |  118.141 |                |