A RegEx i posted in another Thread, may be a bit better suited for your needs:
Var sourceText As String = "v. 15.4 → Naniser 12 8.333"
Var myDouble() As Double
Var rx As New RegEx
rx.SearchPattern = "(?mi-Us)\d+([.,]\d+)?"
Var rxOptions As RegExOptions = rx.Options
rxOptions.MatchEmpty = False
rxOptions.StringBeginIsLineBegin = False
rxOptions.StringEndIsLineEnd = False
Var match As RegExMatch = rx.Search( sourceText )
While match IsA RegExMatch
myDouble.Add match.SubExpressionString(0).ToDouble
match = rx.Search // Fetch the next match
Wend
This one extracts multiple decimals from any string.