All accounts get 7 days (as the parent shows) and all 1TB+ accounts get 7 days + 4 weeks.
However, if you want a custom schedule (say, 30 days, 8 weeks, and 6 months) it only costs more if the space they use exceeds your existing account.
So, if you have a 100 GB account and you use 60 GB and your fancy snapshot schedule (of which the first 7 days is always free) only uses 35 GB ... then there is no additional cost at all.
All accounts get 7 days (as the parent shows) and all 1TB+ accounts get 7 days + 4 weeks.
However, if you want a custom schedule (say, 30 days, 8 weeks, and 6 months) it only costs more if the space they use exceeds your existing account.
So, if you have a 100 GB account and you use 60 GB and your fancy snapshot schedule (of which the first 7 days is always free) only uses 35 GB ... then there is no additional cost at all.