Retained Fire Crews - how often are they available?

I extracted the following data from the background document  to the consultation on the proposed 2022 reorganisation of fire services in Derbyshire.

There is no clear description of how they define availability, but I presume that this measures the number of times they were successful in mustering the required size of crew in the required time, as a proportion of all fires when they would like to have sent that crew.

Station	% availability from Retained crew 2012-2013	Page in document
Buxton	11.62%	144
Swadlincote	40.68%	214
Ashbourne 2+	42.20%	172
Glossop	43.25%	134
Melbourne	51.69%	214
Clowne	52.10%	261
Clay Cross 2+	60.30%	251
Long Eaton	62.97%	227
Matlock*	63.63%	162
Shirebrook	72.40%	261
New Mills	74.01%	125
Ilkeston	75.65%	227
Whaley Bridge	81.41%	125
Hathersage	83.27%	153
Alfreton	84.19%	204
Staveley	86.55%	239
Crich	86.86%	204
Ripley	89.97%	204
Heanor	90.03%	204
Bradwell	90.79%	153
Chapel-en-le-Frith	91.08%	125
Duffield	95.54%	194
Ashbourne 1+	97.40%	172
Belper	97.65%	194
Bolsover	97.70%	261
Clay Cross 1+	99.82%	251
Dronfield	100.00%	251
Average	74.92%
* Special case as retained crew coverage is from full-time firefighters living in Fire Service accommodation next to station
+Two on-call appliances at same station: presumed to be % of time they can turn out one and both engines
Page 204 says that Alfreton Retained (84%) has 'above average availability when compared with the wider Service'
No data provided for Bakewell (and perhaps others)

Source: "Fit to Respond for Consultation Reference October 2013" - Derbyshire Fire & Rescue Service