How to create a dynamic range if the last cell is empty and the columns have empty cells

Hi again!
I want to create a dynamic range in column K. The static range is Range("K2:K821")
The dynamic range I then use for counA and CountIF
Since the last row in column A always is nonblank, i thought using offset

Sub test()
Dim ws As Worksheet
Dim rng1 As Range
Dim lr As Long

Set ws = ThisWorkbook.Sheets("lista")
lr = ws.Cells(Rows.Count, 1).End(xlUp).Offset(0, 10).Row
Set rng1 = ws.Range("K2" & lr)
MsgBox "Last Row: " & lr
MsgBox WorksheetFunction.CountBlank(rng1)

End Sub

the last row is correctly set to 281, but when I put it in the range, then select row 2821 and only 1 blank cell
please help me out
Thanks in advance
Best regards
//Peter