LNBFs contain an LNBF and a feedhorn device, so manufacturers publish specifications such as f/d ratios due to the need to best match the feed device.
Prime Focus antennas are typically between 0.3 and 0.4, while Offset type antennas generally fall between 0.6 and 0.7 f/d ratio.
If you have an LNBF that claims 0.5 to 0.7 f/d, then it would be pretty forgiving about use on just about ANY offset antenna. As was mentioned earlier, the focal point, where all of the signal concentrates, is much more important than the f/d ratio. Formulas are nice to have when figuring out the "big picture" of theoretical focal distance, as derived from the f/d ratio TIMES the diameter in equivalent units such as inches or centimeters...but the reality is that if you have the correct focal distance from the manufacturer, you should need only to double check that with a tape measure, and then use a signal strength or quality meter to see if signals can be improved by moving slightly in or out from that distance (and tweaking polarity for best match while you are at it).
There is no need for an LNB to claim an f/d ratio, because they are physically connected with a feedhorn element, which itself should have f/d specifications.