Copied data not staying in same row

Hello everyone.
I have a sheet of data that I fill and clear repeatedly. I would like to capture some of that data to a log sheet to maintain a history.
The attached spreadsheet functions 'almost' correctly.
The problem I am having is; if any of the cells are empty in the data it messes up the rows in the log sheet.
This is blender code, where I have taken code from multiple sources and tried to blend them together.

Questions:
How do I maintain row integrity when copying data to log sheet?
What is the purpose of the "a" in this line of code? ""LR = .Range("a" & Rows.Count).End(xlUp).Row)"" It seems like I can change it without affecting anything in the macro.

Functions:
Macro -When I enter the desired date, It should copy some of the data from "existing" sheet to "ExistingLog" sheet, and maintain row integrity.

Current Code:

Sub CpyTest()
Dim LR As Long, i As Long

dateString = Application.InputBox("Enter A Date: ")

With Sheets("Existing")
    LR = .Range("a" & Rows.Count).End(xlUp).Row
    For i = 2 To LR
        If .Range("G" & i).Value = DateValue(dateString) Then
            Sheets("ExistingLog").Range("A" & Rows.Count).End(xlUp).Offset(1).Value = .Range("A" & i).Value
            Sheets("ExistingLog").Range("C" & Rows.Count).End(xlUp).Offset(1).Value = .Range("F" & i).Value
            Sheets("ExistingLog").Range("B" & Rows.Count).End(xlUp).Offset(1).Value = .Range("G" & i).Value
            Sheets("ExistingLog").Range("D" & Rows.Count).End(xlUp).Offset(1).Value = .Range("H" & i).Value
      
        End If
    Next i
End With
End Sub

I have attached a sample spreadsheet..

Thanks
tosteven