In the insurance world, you sometimes see the phrase “L+ALAE Ratio” to refer to the ratio of (losses + expenses) divided by premium. It’s a way to measure profitability for a book of insurance business: how many dollars of loss and expense do you have to pay per dollar of premium earned? Lower is better, and you don’t want that ratio too much higher than 100%, because that means premiums aren’t high enough to cover losses (though investment income can sustain small underwriting losses).
I could see “L+” used as shorthand for “L+ALAE” or “L+ALAE+ULAE,” though admittedly, I’ve never seen that specific shorthand used.