ASP Classic Code Logic using If statements to check inputs from a form - vbscript

Question

I have this code in an ASP page written 20+ years ago. I am trying to update the code an I am having trouble figuring this out:
If Request("SUTyp").Count > 1 THEN
CountCriteria = 0
For intMulti=1 to Request("SUTyp").Count
If Request("SUTyp")(intMulti) <> "*" Then
CountCriteria = CountCriteria + 1
If CountCriteria = 1 Then
SUTypCode = "((tblSU.SUTypCode) LIKE '" & Request("SUTyp")(intMulti) & "')"
Else
SUTypCode = SUTypCode & " OR ((tblSU.SUTypCode) LIKE '" & Request("SUTyp")(intMulti) & "')"
End If
Else
SUTypCode = ""
intMulti = Request("SUTyp").Count
End If
SUTyp is a variable that is coming from a form on the previous page. There is an option (from that previous page) in the select box on the form to 'Select All' or to 'Select Multiple Options'.
<Select name="SUTyp" Size="7" Multiple >
<OPTION VALUE="*" SELECTED>all study unit types
<%
do while (not rsSUType.eof) and (SaveError <> -2147467259)
if rsSUType.Fields("SUTypCode").Value = "*" then
%>
<OPTION VALUE="<%response.write(rsSUType.Fields("SUTypCode").Value)%>" SELECTED>.
<%response.write(rsSUType.Fields("SUTypCode").Value)%>,
<%response.write(rsSUType.Fields("SUTyp").Value)%>
<%
Else
%>
<OPTION VALUE="<%response.write(rsSUType.Fields("SUTypCode").Value)%>">.
<%response.write(rsSUType.Fields("SUTypCode").Value)%> -
<%response.write(rsSUType.Fields("SUTyp").Value)%>
<%
End If
rsSUType.movenext
loop
%>
</Select>
It is then using some data to create a variable (SUTypCode =) for a WHERE clause to query the database. What I don't know is the logic of what it is saying. Specifically:
For intMulti=1 to Request("SUTyp").Count
If Request("SUTyp")(intMulti) <> "*" Then
CountCriteria = CountCriteria + 1
If CountCriteria = 1 Then
SUTypCode = "((tblSU.SUTypCode) LIKE '" & Request("SUTyp")(intMulti) & "')"
I am guessing that somehow the ASP form sets some kind of variable intMulti and uses that for a comparison.
If someone could shed some light on this and so I can re-write it that would be great. This is being created using PHP, so I am just trying to figure out what this means so I can create the equivalent.
Thanks!