Hi Eric,
Your explanation makes sense, I’m thinking just follow on a smaller scale, if I have to many I can pass them onto others on the plot.
Looking at what I have done so far I’m thinking this could be the explanation.
None of the seeds planted on Feb 16 are ready to go outside so the 9 March suggestions are for sowing seed direct into the ground.
I am going to sow 9 march suggestions in green house hoping this will give me 4 weeks between future sowing.
Regards you concern about autumn/winter sowing this seems to be covered later on in the calendar example 31 July.
I am sure we will both have lots of success (& few failures) using Charles calendar and be much wiser this time next year.