In addition to the specified temperature, the manufacturer's recommended development time assumes their recommended agitation procedure. For example, Ilford's "FILM PROCESSING CHART" <
link here> says:
"
For manual processing in spiral tanks and deep tanks, the development times are based on intermittent agitation. With spiral tanks, invert the tank 4 times during the first 10 seconds, then invert a further 4 times during the first 10 seconds for each further minute. Where continuous agitation is used for manual processing (as in a dish/tray or with some types of developing tank), reduce these times by up to 15%. For use in rotary processors without a pre-rinse, reduce the spiral tank development times by up to 15%. A pre-rinse is not recommended as it can lead to uneven processing."