For the B230 fuel filter, the Volvo 700/900 Pocket Data Booklet reference has the torque spec as 15-26 ft-lbs for the Bosch filter, same one used in your 240. 15 is not a lot, so I'd lean closer to 24.

My preference is to do it be feel. It's all about the copper crush washers. My tendency would be to just firmly hand tighten them using a 3/8" ratchet against a combo wrench used as a counterhold then with extra effort try to get an extra 1/16 or so turn to get a crush. As a final check once the system is pressurized I'd probably do a quick wrap of a dry paper towel around the banjo fitting just to be sure.

For more experienced hands, the proper way to do it is by feeling the crush happening and taking it until the crush feels like it's done. After the bolt makes contact with the washer, one should gently turn the bolt, feeling the crush of the washer happening until that magic point where resistance suddenly changes.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now