>>974
set volume n--nは0〜7の数字です。これ1行だけ。

--応用
repeat
set Vol_Level to text returned of (display dialog ツ
"0〜7までの数字を入力して音量調節します" default answer "" with icon 1)
try
set Vol_Number to Vol_Level as number
if Vol_Number ウ 0 and Vol_Number イ 7 then
if Vol_Level does not contain "." then exit repeat
end if
end try
end repeat
set volume Vol_Number