Used flags and their meanings:

Unc2   Uncertainty factor of two
R      Radar-derived value
(      Value based on some assumption
>=     Parameter is greater then or equal to specified value
~      Approximate value
<      Parameter is lower then specified value
<=     Parameter is lower then or equal to specified value 

Flags like 'or 6.760', 'given as 18 to 24', 'hours' or 'low' are verbal expressions.