Help! Lost folder numbers with ZB 5.0

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I recently downloaded and upgraded to Zoombrowser 5.0.

Previously my images were numbered for example 124_2945.jpg

Now, and only with images downloaded since I installed the new version, I find they are numbered img_2946.jpg

Though in the EXIF, and on the camera's LCD display, the file number is 124_2945

I download images directly into ZB using a card reader

I do not understand why this has changed, and I cannot find an option in ZB to change it back. Obviously file numbering with a folder number is a better system as it is both easier to identify an image and less likely to lead to inadvertent overwriting.

Can anyone help?

Thanks.