Hello Xchus,
The two errors you are getting are due to a buffer overflow (-200279) and a timeout (-200284). I expect that the error is being returned by the DAQmx Read call that you are making after the second Countdown.vi.
A buffer overflow will occur if you do not read in samples fast enough for the rate at which you are acquiring. It looks like you have set your application to acquire 1200 samples at a time at a rate of 10 Hz. I'm not entirely sure what your Countdown.vi is doing, but it looks like you are roughly calculating a delay before calling the DAQmx Read case structure. If you are slightly off in this calculation, it is possible that you are waiting slightly too long in each iteration of the application and an excess amount of data is slowly building until you get an overflow after ~200 iterations. Two options to prevent this include:
1) Not wiring the 'Samples to Read' input on the DAQmx read so that all available data is read and
2) Use a property node to determine when to read the samples out of the buffer as explained in this Knowledge Base.
A timeout (-200284) will occur if you call the DAQmx read and there are not enough samples available after waiting the designated time ('Timeout' input to DAQmx Read.vi). Following the same above suggestions you can avoid getting a timeout error. The default timeout is 10 seconds. You could also increase this number. Given your sampling rate and number of samples, your application could take up to 120 seconds or 2 minutes to acquire enough data. For more information on resolving the timeout, please read Why Do I Get Error -200284 When I Set a Small Sampling Rate in DAQmx?
Hope this helps,
Jennifer O.
Applications Engineer
National Instruments
LabVIEW user groep 
