Range of values for TX power

For the transmission power, are we allowed to use any number in the range [-30, 4] or only the values specified in table 37 in the product specification? When we select one of these values, what value do we use for the tx level in the advertising value? It isn't going to be the same value, is it? I'm confused, because according to my measurements with nRF 51822 Beacon kit, tx power at one meter is -54, which is clearly not in the aforementioned range.

Thanks

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