Max data age is actually in seconds?

[bjornekelund]

The text in the config file says

# Maximum age of data to report, in multiples of the mode's time frame
#   e.g., for FT8, 15s * 10 = 150s. Data older than 150 sec is dropped 
#   Data is dropped at 260 sec always, regardless of this value.
#   The default value is 10.
#maxdataage=10

When I try to set maxdataage=5, CWSL_DIGI says

### ERROR :: wsjtx.maxdataage must be >= 30

Telling me that maxdataage is actually seconds rather than frames.
But how can then the default be 10? What is the actual default?
And from when is the time counted? At the first sample, at last sample or after decode?

Björn SM7IUN