OK, here are the steps...
1) In Acquire, set up a new sample (unknown), call it "Zircon setup 1", which has Pb Mb on SP3 and Pb Mb on SP4, on peak 900 sec, off peak 260 sec, multipoint acquisition, TDI, on peak time factor 0 0.01, Nth pt 10.
2) In Analyze, add this unknown to setups.
3) Digitize an unknown zircon sample, call it "zircon unknown 1" and run it after assigning "Zircon setup 1" to this digitized sample.
4) When this unknown sample run is complete, display multipoint backgrounds.
5) Edit the multipoint results for "zircon unknown 1" SP3 Pb by changing iterate low from 2 to 3, then assign fit to selected channel for all lines
6) Edit the multipoint results for "zircon unknown 1" SP4 Pb by changing iterate low from 2 to 3, then assign fit to selected channel for all lines
7) Close (multipt. window)
Click analyze in Analyze window
9) In the Analyze window, highlight "zircon unknown 1" and add to setup
10) In Acquire, start New Sample, call it "Zircon setup 2" and Load Sample Setup - choose "zircon unknown 1"
11) Click OK
12) In Acquire, click elements/cations to make sure everything is there OK,
13) In Acquire, click count times. SP3 PbMb is now 900sec on peak, 260 sec off peak as it should be, but SP4 Pb Mb is now 20 sec. on peak, 10 sec off peak.
I tried this without any editing of the multipoint backgrounds and the count times are not affected, that is, both SP3 and SP4 Pb Mb stay at the prescribed 900 sec on peak and 260 sec off peak.