What file format are you using? With some formats such as WAV and single column TXT, the import process looks for the peak then loads from 1500 samples before the peak. Details are on https://eclipseaudio.com/loudspeaker-measurements/
If you know where the peak is, you can indicate it with a number at the end of the filename e.g. “measurement 423.wav”. Or to align time=0 with the start of the file, set the number at the end of the filename to 0. For example “measurement 0.wav”.