Although didn't do a single pull in last six hours, getting a pull rate limit

Hello there, I am trying to understand how the pull rate limit is enforced. I am doing the following:

singularity build my_img.sif Singularity

where the content of Singularity is as follows:

Bootstrap:docker
From:centos:7.4.1708

Although I haven’t done a single pull in the last six hours, I am getting the following:

[root@rc-predict singularity]# singularity build my_img.sif Singularity
INFO:    Starting build...
FATAL:   While performing build: conveyor failed to get: Error reading manifest 7.4.1708 in docker.io/library/centos: toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit

Now, is this limit coming from centos account?
https://hub.docker.com/_/centos