problem with read from serial port

I am trying to receive 2500 bytes via serial port and plot it on a chart, after sending character "S" to the sender device.

I have set the "read count" to 2500 so it is supposed to receive 2500 byte then wait for another "S" but it just receives 101 bytes and then goes to next program iteration. How can I solve this problem?

The VI have been attached.