Laptop booting in BIOS after grub update

I have recently installed Manjaro on my laptop(dual boot with Windows 10). It was working great. It was booting in last opened OS (either Manjaro or Windows) which I wanted to change to Windows by default (for others using this laptop).
I installed Grub Customizer, but it didn’t show Windows option. So I edited grub file in /etc/default and changed set value of GRUB_DEFAULT from TRUE to 2. Because I used to see 4 options when laptop would boot and Windows was 3rd option. So I counted order starting from 0. There was also a timeout of 10s, which I didn’t change. After this change I ran below command -

sudo grub-mkconfig -o /boot/grub/grub.cfg

Now whenever I boot my laptop it boots into bios. I don’t know what went wrong. How do I correct this error.

Please help.