The transmit power of a node can be represented in a logarithmic (dBm) or linear (watts) format, but they represent the same thing.
Online Calculator

Conversion Table

dBm watts
20 0.1
21 0.125
22 0.158
23 0.199
24 0.251
25 0.316
26 0.398
27 0.501
28 0.631
29 0.794
30 1.0

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