This info appears to say they are counting active employees across all companies under the Sage account number. This includes backup companies kept for the purposes of reprinting W2 forms or reviewing older employee info.
Then the price list says ""Payroll tier is determining by the number of paychecks processed for active employees during a pay period"".
The the[ FAQ says](https://www.dropbox.com/s/wrwtz86s73el3qz/Sage%20PR%20Kit_5_Payroll%20Subscription%20FAQs%20Sage%20100%20and%20300_03102016.pdf?dl=0) that there are a bunch of ways to count active employees but in general it's the number of payroll checks issued for employees per pay period. I think.
Expect that Sage will not know the answer to this and they will call order desk dude (who secretly runs most of Sage) but he won't know either though he will guess (wrongly) and once you challenge him any future orders you place with Sage will be slow to process and/or incomplete. BTDT.
For some payroll customers with large numbers of older companies it means that they either go onto unlimited or have to VI and inactivate employees in the backup companies.
I suspect that it will be easier to go unlimited since I suspect the vast number of people using payroll are very close in employee count so that the jump to unlimited is not that great.
The biggest takeaway is that anyone considering purchasing Sage 100 payroll do so before 4/15/2016 so that they can take advantage of the significantly cheaper unlimited ($1,200 for existing users vs $4,000 for new purchasers after 4/15/16).