Resource Management allocation rounded


i've a smartsheet project where i assigned myself on 1,5day (i.e. 12h for the business days from 15 december to 18 december, with 100% effort)

i linked the project to Res. Management, but when i see my allocation on SCHEDULE page, it results that i'm busy for 2 business days

There seems to be no match beetween days scheduled in smartsheet and allocation in resource management.

Any help?