I use the same calculator (in excel), they say that the inoculation should be between 25 - 100, think the reasoning is that too low and you risk the yeast getting overwhelmed or getting infected. Too high and it doesn't grow well.
I've not tested it but my starter have all grown fine and a lot of them have been at the 25 mark as I've also left them a bit long. This meant doing a 2 step starter in a couple of cases. To avoid having to wait on 2 steps to brew a trick I've found is to overbuild by 25 billion cells, if you then pitch the 25 B into a 500 ml 1.040 starter (stirred) it'll land at 100 B cells ready for storage which lets you brew after 1 step and do the 2nd step while the beer's fermenting.
Are you new to starters and/or that yeast? it gets described as true top-cropping, the belgian ardennes strain gets the same description and the 1.5L stirred started kept leaving my 2L flask. I'm going to be growing up the West Yorkshire strain too next week.
To be honest I'm finding this a bit of a faff as I'm trying to keep too many strains going at once. I'm going to try out freezing the yeast so I can defrost a tube and pitch it into a standard 1L (might go 1.5L) starter and it'll be good to go.
Good luck.
