increase size of iso media

src/etc/etc.amd64/disktab

@@ -1,13 +1,13 @@
-#	$OpenBSD: disktab,v 1.12 2014/03/02 15:42:47 deraadt Exp $
+#	$OpenBSD: disktab,v 1.13 2014/03/30 04:56:06 deraadt Exp $
 
 mini34|gzip bsd.rd disk image 3.40625MB:\
 	:ty=SCSI:se#512:nt#1:ns#64:nc#109:\
 	:pa#6912:oa#64:ba#8192:fa#1024:ta=4.2BSD: \
 	:pc#6976:oc#0:
 
-install240|install.fs disk image 240MB:\
-	:ty=SCSI:se#512:nt#1:ns#64:nc#7680:\
-	:pa#491456:oa#64:ba#8192:fa#1024:ta=4.2BSD: \
+install280|install.fs disk image 280MB:\
+	:ty=SCSI:se#512:nt#1:ns#64:nc#8960:\
+	:pa#491520:oa#64:ba#8960:fa#1024:ta=4.2BSD: \
 	:pc#491520:oc#0:
 
 floppy576|3in|3.5in High Density Floppy, 5.76MB:\