Hope the below will make it clear for you:

clear
lcTest = "  0123"
lnTest = VAL(lcTest)
?lntest
lcTest = ALLTRIM(STR(lnTest))
?lctest
lnTest = VAL(lcTest)
?lntest
?STR(lnTest), LEN(STR(lnTest))
?"|" + STR(lnTest) + "|"

>Execute the following code:
>

>lcTest = "  0123"
>lnTest = VAL(lcTest)
>lcTest = ALLTRIM(STR(lnTest))
>lnTest = VAL(lcTest)
>?"|" + STR(lnTest) + "|"
>

>
>Shouldn't the result be |0123|? I can't see how it remains | 0123| after I change it to a string, perform an ALLTRIM on it, and then change it back to a numeric value.