As far as I understand, you only have 6 bytes left in the extended community for specifying the number (2 bytes are used for the type). You can either split those 6 bytes as 2:4 or 4:2. If you specify 'L' after the number, it's treated as 32-bit long (i.e. takes 4 bytes).
In this case 'bandwidth:200001L:37500000' you don't need to specify 'L' for 200001 as it will take 4 bytes anyway (as it's bigger than 65535, the maximum value which can be represented by 2 bytes), so you are left with just 2 bytes for the second number.