diff --git a/text/0001-agile-coretime.md b/text/0001-agile-coretime.md
index 41a061a..a85ea9f 100644
--- a/text/0001-agile-coretime.md
+++ b/text/0001-agile-coretime.md
@@ -122,7 +122,7 @@ A *Region* is an assignable period of Coretime with a known regularity.
 
 All Regions are associated with a unique *Core Index*, to identify which core the Region controls the assignment of.
 
-All Regions are also associated with a *Core Parts*, an 80-bit bitmap, to denote the regularity on which it may be scheduled on the core. If all bits are set in the Core Parts value, it is said to be *Complete*.
+All Regions are also associated with a *Core Parts*, an 80-bit bitmap, to denote the regularity on which it may be scheduled on the core. If all bits are set in the Core Parts value, it is said to be *Complete*. 80 is selected since this results in the size of the datatype used to identify any Region of Polkadot Coretime to be a very convenient 128-bit. Additionally, if `TIMESLICE` (the number of Relay-chain blocks in a Timeslice) is 80, then a single bit in the Core Part bitmap represents exactly one Core for one Relay-chain block in one Timeslice.
 
 All Regions have a span. Region spans are quantized into periods of `TIMESLICE` blocks; `BULK_PERIOD` divides into `TIMESLICE` a whole number of times.