It sounds to me there is more than just the frequencies they specifically mention (that are utilized simultaneously) They indicate available single frequencies plus more....
https://www.minelab.com/usa/knowledge-base/key-technologies#321583
5F×8 (Five Frequency Times Eight) provides five individual transmit frequencies in the one metal detector, selectable at the push of a button. Each transmit frequency optimizes the detector for different size targets and conditions. EQUINOX 800 offers 5 single frequencies of 5, 10,15, 20, and 40 kHz, giving an 8 times range or ratio from 5 to 40, hence the 5F×8 technology designation.
The individual selectable frequencies in EQUINOX 800 are:
•5 kHz - Great for large silver coins
•10 kHz - Good for small Roman hammered coins
•15 kHz - A good general treasure detecting mode
•20 kHz - Ideal for general treasure detecting and gold prospecting
•40 kHz - Optimum sensitivity to very small gold nuggets
Having five selectable frequencies gives the versatility that is equivalent to five conventional single frequency detectors.
Note that EQUINOX Series detectors also feature Multi-IQ technology which allows you to operate all available single frequencies plus more, simultaneously. The option to operate your detector in a single frequency can be helpful if you are experiencing excessive ground noise when using the Multi-Frequency setting.
3F×3 (Three Frequency Times Three) provides three individual transmit frequencies in the one metal detector, selectable at the push of a button. Each transmit frequency optimizes the detector for different size targets and conditions. EQUINOX 600 offers 3 single frequencies of 5, 10, and 15 kHz, giving a 3 times range or ratio from 5 to 15, hence the 3F×3 technology designation.
The individual selectable frequencies in EQUINOX 600 are:
•5 kHz - Great for large silver coins
•10 kHz - Good for small Roman hammered coins
•15 kHz - A good general treasure detecting mode
Having three selectable frequencies gives the versatility that is equivalent to three conventional single frequency detectors.
Note that EQUINOX Series detectors also feature Multi-IQ technology which allows you to operate all available single frequencies plus more, simultaneously. The option to operate your detector in a single frequency can be helpful if you are experiencing excessive ground noise when using the Multi-Frequency setting.