Mesa Boogie F-50 and speaker jacks

On the back of my Mesa F-50 there are 3 output jacks. One is labeled 8ohm and two are labeled 4ohm. I think the labeling is a bit strange. But is it like the F-50 should have at least a 4ohm load and that all these 3 jacks are connected in parallel? (I am planing on connect another speaker cabinet on 8ohm)

The manual pretty much analyzes all of the combinations.

Fast resolve

1 8 ohm cab goes to the 8 ohm jack
2 8 ohm cabs go to the two 4 ohm jacks. Those two are wired in parallel. 2 8 ohm loads in parallel give the 4 ohm load those two signify.
2 16 ohm cabs. Safe mismatch----> connect them to the 2 4 ohm jacks. The amp will see an 8 ohm load instead of 4 and will give a darker looser sound as a result.
1 16 ohm cab connect it at the 8 ohm jack. Same behaviour in a sense with the above.

For other combinations the manual is really good.

Nice recap, giorikas81 - good stuff, thanks!