SYSML21 — Table 30 GBNF Convention is incomplete - does not clarify interpretation of "&element"

Table 30 Graphical BNF Conventions does not define what the production "&element" means. At least one issue resolution (SYSML21-372) intends to use this notation in a different context than what appears in Table 30 ("&element graphical-line &element") so the Table should be updated to explain how this construct is to be interpreted in a scenario other than when a graphical line connects two elements.