Hello Kat,
I assume you're using the TDM plug-in for Excel to view this data based on the format of your excel file. (If you're not, let me know). I believe the problem is in the way you've wired the data from the DAQmx read vi to the Write Data VI. If you place a "To DDT" express VI (from the Express >> Signal Manipulation palette) and select 1D array of waveform as the conversion type, this should fix the problem. Try the VI below.
Hope this helps!