Hi,
The deeming rule applies when you have been resident in the UK for one or more of the three previous tax years and have 3 UK ties and have been present in the UK for more than 30 days without being present at the end of the day (midmight). Only if all 3 conditions are met, does the deeming rule apply and the lower figure on the table get used.
Have a look at the examples at:
RDRM11720 - Residence: The SRT: Days spent in the UK: The deeming rule
If the deeming rules do not apply then the number of days is the second figure based on the number of ties.
Thank you.