I'm no expert but I got a baby Lima shovel nose a couple months ago and it had the same patterns and it grew to be a LSN. But I could be wrong if it's a TSN than you sure are lucky and at 13c
Sorubim lima/elongatus and Pseudoplatystoma tigrinum/fasciatum/reticulatum/etc. are in the same family but are completely different genus. They have different coloration pattern and body shape at all ages - one just needs to look at the photos a bit closer and they will see.
That's like the size mine was when I first got him 2 months ago except i paid $5!! it'll grow fast so be prepared. in 2 months, mine grew from an inch to 5"