CREATE TABLE table_22631 ("[A]  ( mol/L ) " TEXT, "pH" TEXT, "[H 3 PO 4 ]/[A]  ( % ) " TEXT, "[H 2 PO 4 \\u2212 ]/[A]  ( % ) " TEXT, "[HPO 4 2\\u2212 ]/[A]  ( % ) " TEXT, "[PO 4 3\\u2212 ]/[A]  ( % ) " TEXT)

what is the [a] (mol/l) where [hpo 4 2 ]/[a] (%) is 0.612?
SELECT COUNT("[A] (mol/L)") FROM table_22631 WHERE "[HPO 4 2\u2212 ]/[A] (%)" = '0.612'
SELECT COUNT("[A] (mol/L)") FROM "table_22631" WHERE "[HPO 4 2\u2212 ]/[A] (%)" = '0.612'